The story of a 14-year-old girl who won a landmark legal battle to be preserved cryogenically has many people wondering how such technology actually works - for many of us, it seems like something straight out of science fiction.

But sci-fi has a long history of becoming science fact, as outlandish creations inspire real research.
Tractor beams
In Star Wars, the unfortunate heroes are caught in a "tractor beam" that freezes their ship and pulls them towards the enemy. Star Trek has a similar weapon.
An Australian university can do the same thing - although its experiments with lasers could only manage to move a tiny object (one fifth of a millimetre) along about 20cm.
British researchers, meanwhile, have been experimenting with sound waves to shift objects through the air - and can just about manage objects the size of a pea at about 40cm away.
The moon landing
In 1865, Jules Verne published the outlandish novel From the Earth to the Moon, in which three Americans are fired into space in a gun. In his story, the three men launch a lunar vessel called Columbiad, weighing a little under 20,000 lbs, at a cost of $5.5m.
A century later, America did send three men to the moon - in the command module Columbia, which weighed 26,300 lbs, at a cost of $16bn.
To cap it all off, Verne's estimate of $5.5m was equivalent to about $13bn in 1969.
No more needles - the hypospray
In the world of Star Trek (which also predicted flip phones), any ill character is almost miraculously healed by an "injection" from a hypospray - a device with no needles that delivers the cure painlessly, through the skin.
That is a jet injector, and although famous from the TV show, actually predates it. Aaron Ismach invented the jet injector in 1960, six years before Star Trek. It was used for mass vaccinations - especially in the military - since it could be used over and over again. But that brought contamination risks, so it has fallen out of use.
However, the idea hasn't gone away. In 2012, MIT released an updated design for the "hypospray" which can be programmed for many uses, and inject drugs at the speed of sound, which they hope will eventually eliminate the need for needles.
Energy weapons
We're a long way from laser pistols, but a modern energy weapon is the US military's "active denial system", used for crowd control. The non-lethal weapon works like a microwave oven, and causes extreme discomfort as it heats the target's body underneath the skin - and causing the target to flee.
And the Taser personal defence weapon is actually an acronym for Thomas A Swift's Electric Rifle.
Nasa researcher Jack Cover, who created the device, named it after a 1911 book he read as a child, in which the eponymous hero invents a gun that fires bolts of lightning.
Wells and Asimov
Most remarkable of all, perhaps, is the eerie accuracy of a handful of science fiction writers in the 20th century.
HG Wells predicted automatic sliding doors in 1899, and the atomic bomb in his novel The World Set Free, written in 1913 and published the following year.
Isaac Asimov, however, made some startlingly accurate predictions about 2014, in an essay to mark the 1964 World's Fair,
They included global video calling, robots that would "neither be common nor very good in 2014", flatscreen TVs and early 3D and self-driving cars.
Such predictions suggest anything is possible. But there are still plenty of limits on what we can do. Some research, while reported on with incredible headlines, simply hasn't reached any practical application yet.
Invisibility 'cloak'
Whether you're a Harry Potter fan or a space traveller, "cloaking" is often used to refer to invisibility, bending light around an object to make it disappear.
This can actually be done for small objects - if you want to arrange a set of lenses in a precise arrangement, using the Rochester Cloak technique, it can be reproduced at home. But with its strict set up, it's just an optical trick.
Other "cloaking" attempts have been able to hide objects from microwaves or radar, but there's nothing yet that can fool the human eye in practical scenarios.
Power armour
From Iron Man to future dystopia, powered armour for soldiers has always been a staple in sci-fi. The US military is among those with an eye on the idea.
TALOS - that's a Tactical Assault Light Operator Suit - has often been described as an "Iron Man suit", but is far less exotic than the superhero's attire.
Instead, the US Army hoped to create a "smart" bodysuit, which monitors soldiers' vital signs, with a powered exoskeleton to increase strength.
The project is rumoured to use liquid armour which solidifies when hit by bullets - but very little is known about its progress.
Teleporters
The "transporter", a staple of sci-fi, is probably impossible. But that doesn't stop it making headlines.
In a process called quantum entanglement, a change made to one particle in lab conditions can affect another one, some distance away. It's a way to send information from one place to another, without it travelling in the space between, hence "quantum teleportation".
But the particles involved - qubits - are information only, and there's no evidence that it can be used for atoms, molecules and certainly not people - but it could lead to a futuristic internet.
Warp drive theory
In Star Trek and many other films and television shows, "warp drive" is a way to travel faster than light (which should be impossible) by bending space around a spacecraft.
The closest we have is called an "Alcubierre drive", after the mathematician who proposed it.
The idea is to shrink space in front of the ship and expand space behind it - so the ship itself never has to travel at light speed.
But it has so many practical problems it may never actually exist, and Nasa generally considers it impossible - despite the occasional piece of research on the topic.


London Scottish have delayed pre-season training as they lack players because of their cancelled partnership with Scottish Rugby, centre Alex Grove said.

Under the joint venture, the union (SRU) had pledged to supply Scottish with young players and coaches.
"It's really not a great situation," Grove, 28, told BBC Scotland.
"They've got to find half a squad from somewhere at a time of year where everyone's sort of signed up elsewhere."
The two parties announced on Monday that the initiative had been ended just five months after it had been announced.
Grove, who was on loan at Scottish earlier this season, had sympathy for the club but questioned their approach.
"I feel sorry for London Scottish that the deal's been pulled, but I don't think they've done themselves many favours," he said.
"They've allowed a lot of senior players to leave on a promise they're getting these young guys.
"If I'm the SRU, I'm then thinking, do I want to be sending a load of young guys down there to create an academy side?
"Do we want to create an under-23 side, essentially, struggling at the bottom of the league?
"Possibly the SRU questioned London Scottish's ambition. Do they really have a squad, the firepower capable of pushing for top-four play-off spots?"
Scottish Rugby suggested on Monday that its board felt "the performance environment in place was not sufficiently developed to offer the player pathway we had envisaged".
Exiles president Rod Lynch criticised the decision, while chairman Sir David Reid was irked that the number of players provided had been cut from 14 to 10, and "none of them senior players".
Former Glasgow Warriors head coach Sean Lineen had been appointed director of rugby, with former Edinburgh back-row Roddy Grant joining the coaching staff until the end of the season, bringing "a clear shift in focus", and energising the squad, according to Grove.
Neither will be a part of the set-up in the forthcoming season.
Grove, who has been released after 10 years with Worcester Warriors and won three caps, believes the Scottish player development pathway, as well as the club itself, could suffer.
"Robbie Fergusson and George Horne, when I was there, those two guys, who are possibly blocked at the moment at Glasgow, have come down and been excellent," Grove said.
"They've really benefited from regular rugby. They're young, enthusiastic, full of energy. More importantly, they're willing to learn, grow and challenge themselves.
"Imagine having 12 players like that; the club would be in a far better place."
Grove fears Scottish, who finished eighth last season but reached third place in 2014-15, will struggle to compete in the forthcoming campaign.
"They were meant to start pre-season yesterday and that's had to be delayed because of the lack of players in the squad," he said.
"It would be frustrating as a player to be in the middle of this - the guys that were going to come won't get rugby at that level and the guys they signed on that thought they were going to have that partnership are going to be frustrated.
"They would have had a squad they felt could have competed for the play-offs and now, with the young guys not coming and the old guys leaving, they've barely got 15 guys."


The SNP and Labour have clashed over waiting times at Scotland's hospitals.

The SNP said Scotland's NHS had outperformed the rest of the UK on accident and emergency waiting times, which it insisted had "improved dramatically" in 2015.
However, Labour said there were "hidden waiting lists" among patients taken to separate "immediate assessment units".
The two parties have frequently traded blows over NHS performance in the build-up to May's Holyrood election.
Figures show that 94.5% of patients visiting Scotland's core A&Es in December 2015 were seen within the target time of four hours.
However, Scottish Labour said there were up to 30 different "immediate assessment units" across the country, wards which patients can be sent to where there are different waiting times targets or even no targets at all.
The party's public services spokesman Dr Richard Simpson said these amounted to "hidden waiting lists", and pointed to newspaper reports from November 2015 that a patient had died while waiting for treatment in one such ward.
He said: "These are wards filled with patients who a doctor has judged sick enough to go to hospital, but these patients face a postcode lottery in terms of the care they will receive.
"There isn't a consistent name or a consistent waiting time target in any of these wards.
"It cannot be right that the length of time a patient waits for treatment is measured if they go through one door in a hospital but not another."
SNP MSP Dennis Robertson said there had been a 178% increase in A&E consultants on his party's watch, and English A&E performance had fallen "well behind Scotland".
He said: "Scotland's A&Es have made real progress in the last year, and that is a testament to the hard work of the record number of NHS staff up and down Scotland.
"And while there is still work to do, Scotland's A&Es are now consistently the best-performing in the UK.
"The SNP sees Scotland's NHS as one of our nation's most important assets and we will continue to do all we can to support our hardworking healthcare workers to provide the best possible care for all patients.
"Our government in Scotland will continue to increase NHS frontline investment in at least real terms for every year of the next parliament if the SNP are re-elected."


Two men who died after they fell from a balcony at Cadogan Square in west London have been named by police.

Tomasz Procko, 22, and Karol Szymanski, 29, had been delivering sofas to the Knightsbridge property on Friday morning when the balcony collapsed.
Mr Procko, of Greenford, west London, died at the scene while Mr Szymanski, of Wembley, north-west London, died later in hospital.
Both men were originally from Poland. Their next of kin had been informed.
Eight other people were treated for injuries, the London Ambulance Service said.
A neighbour, who wanted to remain anonymous, told BBC News: "They were trying to pull a couch up to the first-floor apartment with ropes.
"[It] was apparently too heavy. The fence broke off and fell on the workmen below."
Sinclair Johnston, an engineer who has worked on another property in the square, said the decorative railings could not be depended upon to support weight.
The decorative wrought-iron railing appeared to have fallen about 3.6m (12ft) to the ground, although the stone base of the balcony appeared undamaged.


A fibreglass sculpture of a cow stolen from a beauty spot just before a charity auction has been found.

Cycling Moo Kay was one of 60 decorated cows that made up last summer's Surrey Hills Cow Parade.
It was taken in August from its plinth at the top of Box Hill, near Dorking, which formed part of the London 2012 Olympics cycling road race course.
The sculpture was found at a property in Newdigate by police. A man in his 40s was arrested on suspicion of theft.
The artist who painted it, Charlie Rowbotham, said he was delighted it had been found.
A charity auction of the cows in November - excluding Cycling Moo Kay - raised more than Â£130,000 which was to be split between 52 charities.
Cycling Moo Kay has now been been returned to organisers at Surrey Hills Cow Parade.


The son of Etienne Tshisekedi, the Democratic Republic of Congo's late opposition leader, has been chosen as his father's successor.

Felix Tshisekedi, 53, will now lead the opposition coalition in crucial negotiations over the departure of President Joseph Kabila from office.
Under a deal agreed last year, new elections would be held by the end of 2017 and Mr Kabila would not run.
It followed deadly protests calling for the president to step down.
Mr Kabila's final mandate ran out in November 2016.
Not everyone in the opposition coalition is happy with the choice of the younger Tshisekedi as leader, with some openly criticising his lack of senior political experience.
"Where else in the world would someone be put in charge of such an important process... who has only been in the opposition for seven months," coalition member Joseph Olengankoy told BBC Afrique.
The UDPS party of Mr Tshisekedi senior has not yet announced a new leader, although it is part of the alliance now lead by his son.
The veteran opposition leader died in Belgium earlier this year, aged 84.
His body is due to be flown back to Kinshasa on 11 March.
His appointment also comes at a time when there are fears that the government may be trying to retreat from key aspects of the transition deal.
Last month, the budget minister said the cost of organising polls in 2017 was too expensive, throwing the election timetable into doubt.
Mr Tshisekedi's appointment means that he is now more likely to be made prime minister in a power-sharing government, a post due to be held by an opposition figure under the terms of the deal.
DR Congo has never had a smooth transfer of power since independence more than 55 years ago.
Mr Kabila took power in 2001 following the assassination of his father, Laurent Kabila.
He has won two elections and the constitution bars him from running for a third term.


Precautions against the spread of bird flu in Northern Ireland are to be extended for a month.

The Avian Influenza Protection Zone will remain in place until 31 May, the Department of Agriculture has announced.
Chief Veterinary Officer Robert Huey called on poultry keepers to remain vigilant against the spread of the disease.
"The risk of infection from wild birds is decreasing," he said.
"It is essential that bird keepers comply with the biosecurity requirements set out in the declaration of the Prevention Zone if they are to minimise the risk of infection."
Measures to ensure that poultry are kept separate from the wild population were introduced on 17 March.
According to the department, the threat to public health from the virus is very low and consumers should not be concerned about eating eggs or poultry.


University staff are to stage a one-day national strike at the end of this month in a row over pay.

Institutions across the UK are expected to be affected by the action, taken by three unions - the University and College Union (UCU), Unison and Unite.
The Universities and Colleges Employers Association (UCEA), which represents universities as employers, said it was disappointed by the move.
The news comes as teachers plan a strike in parts of England on Thursday.
Members of the National Union of Teachers and the NASUWT  are staging a further regional strike in their continuing row over pay, pensions and workload.
The unions planning the university strike for 31 October claim  a 1% pay rise offered to  staff - including lecturers, technicians and administration workers - means there has been a 13% pay cut in real terms since October 2008.
For Unite, the turnout for the ballot was 28% and of these, 64% (1,654 members) voted in favour of action. For the UCU the turnout was 35%, with 62% voting in favour of strike action.
Unison declined to release details of what percentage of its membership had voted. It only said of those who had voted, 54.4% had been in favour of action and 45.6% against.
UCU head of higher education Michael MacNeil said: "Staff have suffered year-on-year cuts in the value of their pay. Quite simply, enough is enough.
"We urge the employers to reflect on the fact that they are about to face their first ever strike by three unions at the same time and come to the negotiating table to resolve this dispute.
"The suppression of academic pay is one of the most sustained pay cuts since World War II and, while strike action is always a last resort, the fact that staff are prepared to take this step demonstrates just how angry they are."
A spokesman for UCEA  said: "Employers do understand that the general 1% uplift offered to all may be frustrating to these trade unions, with 5% of the workforce saying they will support strike action.
"However, we also know that much more than this is going into pay increases for HEI [higher education institution] staff: 3% incremental rises for many plus merit payments beyond this.
"Our HEIs tell us that the vast majority of their staff understand the reality of the current environment and would not want to take action that could harm their institutions and their students."


The MTV Europe Music Awards are to be held in London for the first time in more than 20 years.

"I'm thrilled to confirm that the @MTV European Music Awards are returning to London," announced mayor Sadiq Khan on Twitter.
The event will take place at the SSE Arena in Wembley on 12 November.
The awards, now in their 24th year, were last held in London in 1996, with Oasis and the late George Michael among the winners.
Other UK cities to have hosted the event include Edinburgh, Liverpool, Belfast and Glasgow.
Last year's ceremony, in the Dutch city of Rotterdam, featured performances from Green Day, Bruno Mars and Kings of Leon.
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A shot peregrine falcon has been rescued by a "good Samaritan" who found it in distress by the roadside in Greater Manchester, police have said.

The man spotted the injured bird by the A580 near Leigh on Friday and rushed it to a vet in Bolton.
Det Con Randolph Lyle said the falcon had been "shot with a shotgun" and appealed for anyone with information about the shooting to contact police.
Peregrine falcons are protected under the 1981 Wildlife and Countryside Act.
Mr Lyle said the bird had been receiving treatment for its injuries and would be released back into the wild once it had recovered.


Chinese authorities will limit the operations of North Korean airline Air Koryo, after a Beijing-bound flight made an emergency landing last month.

The flight from Pyongyang had to land in the North-eastern Chinese city of Shenyang because of smoke in the cabin. No one was injured in the incident.
China's Civil Aviation Administration announced "relevant measures to limit operations" without giving any details.
The state-owned airline was also told to improve training and maintenance.
Most of Air Koryo's international flights are to China, with a few scheduled flights to Russia.
"China has become a little bit more active recently in naming and shaming airlines that make mistakes," Greg Waldron of Flightglobal told the BBC. "And we've noticed a recent pick up in that."
"The North Korean airline would likely be a very resource-deprived airline, operating a number of older airplanes. And often, that older equipment is difficult to maintain. By international standards it would not be a great airline."
The Chinese aviation regulator did not give any details on the measures it would impose but Mr Waldron thinks it's unlikely there would be a ban on flights or even a fine for the North Korean carrier.
"It's really hard to say exactly what they could do. Anything between North Korea and China is very difficult because it's always also political."
Britain-based airline ratings website Skytrax lists the carrier as the world's only "one star" airline, though its rating does not measure safety standards.
Though by no means a tourist airline, Air Koryo is the main way that visitors to North Korea can enter the country.
Simon Cockerell of Beijing-based Koryo Tours, a leading independent tour agency focusing on North Korea, told the BBC that he doubts the new development would have an impact on tourism.
"Our guests are generally happy with the airline. And they mostly fly at least one route with Air Koryo, some take the train on the way back. They do some research and then aren't put off by that Skytrax ranking which has nothing at all to do with safety standards."
Air Koryo is North Korea's only airline and was established in 1950. The airline has only a small fleet, mostly consisting of Russian-built Tupolev and Ukrainian Antonov aircraft, for its international flights.
The service from Pyongyang to Beijing uses a Russian Tupolev Tu-204, a medium-range jet airliner that can carry about 140 passengers.
"The oldest planes they are using on international routes are from 2008," Mr Cockerell explains. "For their Antonov planes built in Ukraine for instance they have Ukrainian technicians doing the maintenance."
On domestic routes however, older Soviet-era aircraft are still used, some of which are so old that aviation enthusiasts can book specialised tours to experience flying in aircrafts dating back to the early days of the Cold War.


Ryan Giggs has been named as one of the stars involved in a highlight of the Champions League Festival in Cardiff Bay.

The former Manchester United and Wales midfielder is one of 25 European football legends taking part in the ultimate champions match on a floating pitch on 2 June.
The free festival will run alongside the Champions League finals.
It runs from 1-4 June and is expected to attract over 200,000 people.
The women's final will be held on 1 June at Cardiff City Stadium and the men's final on 3 June at the Principality Stadium.
Both kick off at 19:45 BST.
More players for the ultimate champions match are to be announced next week.
Guide to Champions League in Cardiff
Champions League 'city's biggest event'
Champions League 'ring of steel' in city


Plans to build a £200m tidal barrage in Lancashire that will power tens of thousands of homes have been announced.

Natural Energy Wyre Ltd said the Duchy of Lancaster has given it an exclusivity deal to create the UK's first tidal energy power station.
If approved, it will be built on the Wyre estuary, which belongs to the Queen in her role as Duke of Lancaster.
The Royal Society for the Protection of Birds said it had concerns about how the scheme could affect wildlife.
Natural Energy Wyre Ltd said it now needed to find £10m to proceed with a formal planning application.
It said the power station would support the government's renewal energy objectives, create thousands of jobs and attract 600,000 visitors to the region, as well as help with flood defences.
A barrage, which would span the mouth of the river with six turbines, would take three years to build, the firm said.
It will produce renewable energy four times a day, on the turn of the tide, for more than 100 years, Natural Energy Wyre Ltd added.
Graeme Chalk, head of project management for the Duchy of Lancaster, said the tidal barrage would "provide a source of green and affordable energy for many years to come".
Tim Melling, RSPB senior conservation officer, said: "Climate change is the biggest threat to the natural environment so it's vital we invest more in renewable energy. But tidal barrages are not the right option and this proposed scheme on the Wyre would cause major damage to the estuary.
"A barrage would knock the tidal system out of sync and destroy this prime feeding habitat by reducing the size of the feeding areas and making them available for less time."


Ireland have reported no fresh injury worries following their 28-22 World Cup warm-up win over Scotland at the Aviva Stadium in Dublin on Saturday.

Simon Zebo limped from the field, to be replaced by Paddy Jackson, with three minutes remaining, but the Munster back was not mentioned as being an injury concern in Monday's medical bulletin.
The squad has been released for a week and will reassemble on 23 August.
Their third warm-up game is against Wales in Dublin on Saturday 29 August.
Ireland beat the Welsh 35-21 in their opening preparation game for the World Cup in Cardiff on 8 August.
Ulster winger Andrew Trimble missed the victory over the Scots with a foot injury but is making good progress in his recovery, while the medical team continue to monitor Cian Healy as he recovers from neck surgery.
Prop Marty Moore could feature for Leinster against Ulster in a friendly in Belfast on Friday as he continues to recover from shoulder surgery.
Ireland face Canada in their first World Cup Pool D game in Cardiff on 19 September.


Ally McCoist has left his position as Rangers manager and the Scottish Championship club say he is now "on gardening leave".

The 52-year-old handed in his resignation earlier this month and had started his 12-month notice period.
McCoist remained in charge of the team for the defeat by Queen of the South and Saturday's win against Livingston.
"Assistant manager Kenny McDowall will take over his duties until the end of the season," a Rangers statement read.
"We would like to thank Ally for all his hard work and dedication over the last few years, but we feel it is now in the best interests of all parties to move on."
McCoist, who had been in charge at Rangers since the summer of 2011, was called to a meeting at Ibrox on Sunday by chief executive Derek Llambias and chairman of the football board Sandy Easdale.
He was told it would be best for the club if he stood down and was placed on gardening leave. The search for a new manager is under way but McDowall will take charge of the side in the meantime.
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Rangers are nine points behind Scottish Championship leaders Hearts and the Tynecastle side can extend their lead to 12 points if they beat Cowdenbeath on Tuesday.
Pressure on the Ibrox boss intensified after a surprise 3-2 defeat by part-timers Alloa Athletic in the Petrofac Training Cup semi-final and, following the defeat by Queens, the manager admitted Hearts were now "strong favourites" for the Championship title and automatic promotion.
McCoist was believed to have become alarmed at the number of staff losing their jobs at the club.
Bellshill-born McCoist was a Rangers player for 15 years as well as playing for St Johnstone, Sunderland, Kilmarnock and Scotland, for whom he won 61 caps.
He had been assistant manager at Ibrox under Walter Smith and stepped up as his successor while Rangers were still in the Scottish Premier League.
Administration and subsequent liquidation of the former company that ran the club resulted in Rangers playing in the fourth tier of Scottish football.
A high turnover of players ensued in 2012 and McCoist led the side to two consecutive league titles to get Rangers into this season's Championship.
And, following the recent losses to Queen of the South and Hearts and confirmation of his resignation, McCoist said he was "not sure" whether he would attend Monday's annual general meeting at Ibrox.
Former St Mirren player McDowall joined Rangers as first-team coach under Smith in 2007 and was promoted to assistant manager when McCoist became manager.


A 44-year-old man has been charged with trespass and possession of a knife after being arrested at Buckingham Palace, Scotland Yard has said.

David Belmar, from Haringey, north London, will appear in custody at West London Magistrates' Court on Tuesday.
Police said a man had tried to enter the palace through its north centre gate at about 11:30 BST on Monday.
The man was arrested and taken to a London police station. Buckingham Palace said the Queen was not at home.
Police said in a statement that the knife was found after the man was searched, adding that no-one had been injured during the incident.
The north centre gate is the one furthest to the right in the commonest view of the palace, looking from the Victoria Memorial. It is the entrance to the palace that is in everyday use.
The incident follows the arrest last month of a man on suspicion of burglary, trespass and criminal damage after police said he had scaled a fence to get into Buckingham Palace.
A second man was arrested outside the palace on suspicion of conspiracy to commit burglary. Both remain on police bail.
Security at the palace has been breached on a number of occasions, most famously by Michael Fagan in 1982 when he broke into the Queen's bedroom.


Dover Athletic have re-signed former captain Connor Essam on loan from League Two side Leyton Orient until the end of the season.

The 23-year-old defender played 42 games for the Whites prior to joining Orient in July 2015.
Essam, who has made 26 appearances for Orient this season, last featured in their 1-0 win at Oxford on 12 March.
He could go straight into the side when Dover Athletic play host to Torquay United on Saturday.


Thousands of people have marched in Warsaw, protesting against Poland's conservative government, 27 years since the fall of communism.

Opposition leaders, including two former presidents, led the rally against what they describe as the government's anti-democratic policies.
The ruling Law and Justice party has been criticised by the European Union over its reforms of the judiciary, surveillance, and media laws.
The party rejects the accusations.
Saturday's demonstration in the Polish capital was organised by Committee for the Defence of Democracy (KOD).
People blew horns and waved both Polish and EU flags as they walked through central Warsaw.
The opposition said about 50,000 people took part in the protest. Police estimated about 10,000 people were on the streets.
Former Presidents Aleksander Kwasniewski and Bronislaw Komorowski were among the protesters.
The participants wanted to celebrate the end of communism after 4 June 1989 elections.
But they also wanted to voice their opposition to what they see as the government's backsliding on democracy, the BBC's Adam Easton in Warsaw reports.
The Polish government passed legal amendments late last year which change the way the Constitutional Court operates.
The changes require a two-thirds majority of the 15 judges to support a ruling for it to be valid, and also stipulate a quorum of 13 judges for rulings to be valid.
Critics have said the changes mean the court is now unable to examine government legislation.
The European Commission and the  Council of Europe say the changes undermine the rule of law.
Recently approved media laws have also placed public radio and TV under a new national media council and have given the treasury minister the right to hire and fire management.
Despite the criticism, the government is trouncing the opposition in the polls thanks to a sharp hike in child benefit payments, a plan to build cheap housing and its outright refusal to take in Muslim migrants, our correspondent says.


An arrest has been made after a cyclist died following a collision with a car in north-west London.

The 50-year-old cyclist collided with the car just after midnight on Forward Drive, Harrow and suffered serious head injuries.
Paramedics tended to him but he died an hour later at the scene.
The driver of the car, a 30-year-old man, has been arrested on suspicion of causing death by dangerous driving and is being questioned by police.


(Close): US stocks closed lower as investors assessed mixed earnings reports and data showed durable goods orders slipped in September.

The Dow Jones industrial average closed 0.24% lower, to 17581.43 points, while the S&P 500 lost 5.29 points, or 0.26%, to 2,065.9 points.
The Nasdaq composite index closed 0.09% lower, to 5030.15 points.
Chinese online retailer Alibaba said second-quarter sales rose 32%. The shares rose 4.01% to $79.41.
That beat analyst estimates, even though the value of goods traded grew at a slower pace.
But Ford fell 5.13% to $14.88, after reporting sharply higher quarterly profit, helped by a good performance in North America, but missed Wall Street estimates because of higher taxes.
The Federal Reserve is beginning its two-day meeting. Few analysts expect the central bank to raise interest rates because US inflation is low and the economic recovery remains uneven, but analysts will be looking to see if any clues emerge as to the timing of a rate rise.
Figures from the US Commerce Department showed orders for durable goods dropped 1.2% in September. The department also said orders fell 3% in August, an even bigger dip than first reported.


Republic of Ireland full-back Stephen Ward is a fitness doubt for Sunday's Euro 2016 game against France but Jonathan Walters may return to action.

Burnley defender Ward, 30, injured an ankle in the first half of Wednesday's dramatic 1-0 win over Italy.
The left-back missed training in Versailles on Friday morning.
On the plus side, Stoke striker Walters resumed training with the squad after missing the last two Euro 2016 games because of an Achilles injury.
On Thursday, manager Martin O'Neill said Ward's ankle had "blown up" after he picked up the knock in the first half of the game in Lille.
O'Neill is likely to be keen to retain Ward at left-back and allow Wednesday night's goal hero Robbie Brady to be used in the more offensive role he adopted to such good effect against the Italians.
The Republic players were back in training on Friday morning after being given the day off on Thursday.
O'Neill and his players did not get to bed until around 4.30 in the morning on Thursday after travelling back from Lille to their base in Versailles.
Inevitably, the pre-match discussion about Sunday's game in Lyon includes mention of the Republic having the chance to avenge the incident in November 2009, when the Irish missed out on qualification for the World Cup finals in South Africa thanks to a decisive goal that saw Thierry Henry handle the ball in the build-up.
However, O'Neill says the current Republic squad have "decided to forget about it".
"It will be a talking point obviously but I don't think it will concern us when we play the game," added O'Neill.


Wales men's hockey team beat Poland in their opening game in the of the World League 2 tournament.

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Goals from Gareth Furlong, Luke Hawker and Rupert Shipperley secured the win in Belfast.
They play Scotland on Sunday before facing France in their final group game on Tuesday,
A top-two finish in the eight-team tournament would lift them in the rankings and give them a chance of a first World Cup appearance.
The World League is a series of tournaments held over a two-year period with the latest edition running from Saturday 11 to Sunday 19 March in Belfast.
The final group standings decide the knockout fixtures and the two teams who reach the final will go through to the next round of the World League in London in June.


Thousands of migrants are currently living in camps known as "the Jungle" on the edge of Calais in northern France.

The population of the camp has risen steadily in recent weeks to about 2,500, including about 250 children, according to medical volunteer group, Medecins Sans Frontieresâ€Ž (MSF).
Youth worker Liz Clegg has been working with women and children in "the Jungle" for several months.
She first visited the region to deliver camping equipment donated by  festival goers at last year's Glastonbury Festival, but ended up staying to work with unaccompanied children aged between 10 and 13.
She told BBC News why she thinks it is important that the UK offer these children sanctuary.
"I work in a centre which was built for refugees by a group of volunteers from Ireland. The 10 to 13-year-olds that I work with are wonderful but they do have serious behavioural problems.
This is where the journey ends for many - and hope ends.
Children arrive with horrendous stories, but they are still full of life when they arrive. They stay here for three months and deteriorate, as they slowly come to realise that they may never get to Britain.
They are brainwashed that getting to the UK is the only thing that matters and that on their journey to the UK they must have nothing to do with authority and not get their pictures taken.
But these are children as young as 10. They are not capable of making this decision and they have no adults to help them.
We try to dissuade them from going onto the lorries, but it rarely works. These children are out every night trying to get to Britain. They come back cold, and tired and with no one to care for them.
I am seeing children crack.
Earlier this week one of the children was so upset that he was howling like a dog and fainting. He has no one here.
Another child, who was really chatty when he first arrived, is now unresponsive to anyone.
Some of the children pretend they are accompanied. They say they travelled here with an uncle, but after talking to them you soon realise that the uncle is normally an adult who they met on the journey rather than a blood relation.
When they get to Calais this adult often abandons them to get on a lorry to the UK.
The youngest child I have worked with is 10-years-old. He was separated from a family member on the journey from Afghanistan.
Most of the children in this age-group seem to come from Afghanistan but I've worked with Syrians, Kurds and children from Eritrea over the past few months.
I strongly believe that if we are going to take child protection seriously then we need to look at the children in Calais, and not just the camps around Syria. Especially the young ones.
They are little and miss their families and they have no one."
Interview by Hannah Henderson.


More than £200,000 has been awarded to families after a fatal outbreak of Legionnaires' disease.

Richard Griffin, 64, William Hammersley, 79, and Harry Cadman, 71, died in the summer of 2012 while many others were affected.
A hot tub on display at the JTF warehouse in Stoke-on-Trent was the "probable source" of the outbreak, the Health Protection Agency said.
JTF declined to comment on the settlement.
Mr Griffin's daughter, Rachel, who now lives in Cumbria, said she was relieved compensation had been agreed without the need for a court battle.
"Nothing can ever bring our dad back but we just wanted to make sure that justice was done and that there was some accountability for his death," she said.
"I truly hope no-one ever has to go through what we have."
The outbreak struck more than 20 people in the summer of 2012.
Mr Griffin contracted the disease while delivering meat to a café in the JTF Warehouse.
He initially suffered headaches and hallucinations and later lost consciousness at his home in Clayton. He died in hospital from multiple organ failure.
The Health Protection Agency confirmed the hot tub on display at the JTF Warehouse, off King Street in Fenton, contained the same strain of Legionella as those who had become ill.
Inquests are set to take place next year and the Crown Prosecution Service has not yet decided whether to pursue charges.
Irwin Mitchell, which has been representing affected families, said JTF had admitted civil liability.
"Nothing can turn back the clock but we are pleased to have finally concluded these cases, allowing those families affected to begin to move on with their lives," said lawyer Amandeep Dhillon.


Nearly one in five museums has introduced charging in the last year or will do so this year, according to a survey by the Museum Association.

The survey also revealed that 18% of UK museums have had to close a part or branch of their museum in the last year or will have to do so in 2016.
The Association said the changes were due to cultural spending cuts for local authorities.
More than 40 museums have closed across the UK since 2010.
That number is expected to grow in 2016, following recent announcements that museums in Lancashire, Durham, Dudley and Leicestershire will have to shut.
Nearly half of respondents - 45% - also said they had increased the number of voluntary staff, compared with 32% the previous year.
There has been a 28% cut in cultural spending by local authorities since 2010.
The Museum Association's findings showed that overall public funding to museums decreased by 2% and income from grants and donations fell by 4%.
The further cuts in local authority funding announced in the recent Spending Review mean that cultural spending by local authorities is set to fall further over the next five years.
The government has made a commitment to keep entry to national museums free but this does not cover the vast majority of museums in the UK.
A spokesperson for the government's Department for Culture, Media and Sport told BBC News it was committed to supporting the UK's cultural institutions, which very firmly included museums.
"One of the best investments we can make as a nation is in our extraordinary arts and museums," said the spokesperson.
"That is why this government has protected funding for national museums to ensure they remain free to enter and secured a cash increase to Arts Council England.
"Councils will have almost £200bn to spend on local services - including museums - over the lifetime of this parliament."
Last year however both Brighton Museums and York Art Gallery introduced charges for entry.
Five Lancashire museums are set to close, including two mill museums, Queen Street Mill and Helmshore Mills Textile Museum.
Sarah Hardy is a former member of staff at Helmshore - she is campaigning for more time to find alternative ways of keeping the museum open.
"We lose our heritage, our local heritage but also our national and even international heritage (if Helmshore closes). Lancashire has a rich industrial heritage... if we lose it, then we have lost it forever, these sites are so unique... they can't just be replaced once they've gone."
Financial pressure is also having an impact on museum collections, with 11% of all museums considering selling off items for financial reasons, up from 9% in 2014.
The survey also showed that museums in northern England, Wales and Northern Ireland reported larger year-on-year decreases in public funding than those in the Midlands, southern England and Scotland.
Sharon Heal, director of the Museums Association, said: "Museums that serve local communities deliver real public benefit and there is a danger that whole areas of the country will have these services wiped out if the cuts continue. The MA will continue to advocate for all museums and the life-changing experiences that they can provide."
Lancashire County Councillor Marcus Johnstone, cabinet member for environment, planning and cultural services, said: "I did not come into politics to close museums or any other public service but the government has continually cut the county council's funding and this is the reality of our situation."
However 61% of museums surveyed reported an increase in visitor numbers year-on-year.
And despite the cuts, museums are fighting back with self-generated funding, with retail sales up 6%.
The Museums Association is the largest membership organisation representing museums and galleries in the UK and the people who work for them.
Between September and October 2015, the Museums Association asked museums to provide information regarding changes to their budgets, staffing operations and general service provision.
The survey was answered by 115 museums, representing all types of museum and all areas of the UK.
There are more than 2,500 museums in the UK.


The UK was late to recognise the need to tackle the extremist views behind terrorism, the foreign secretary says.

Philip Hammond also said there had been a reluctance to "recognise the link between non-violent extremism and violent extremism" in the past.
He said the importance of tackling all forms of extremism was now realised.
Addressing a security summit in Bahrain, Mr Hammond described countering Islamist extremism as "the great challenge of our time".
In the speech, in Manama, he said: "We in Britain, have recognised - perhaps later than we should have - that to prevail in that struggle, we have to tackle all forms of extremism, not just violent extremism."
He added: "For decades we have clung to a false distinction between the two.
"We have tolerated - in fact we've even celebrated in the name of multiculturalism - ideas, behaviours and institutions that have encouraged separateness of identity and intolerance of difference.
"With hindsight, we've been too tolerant of intolerance.
"Too anxious about causing offence instead of standing up for what is right and tackling head-on the radicalisers and the extremists peddling their messages of hatred and division."
Mr Hammond said details about British strategy in the Gulf would be published in the coming months.
He was also in Bahrain to take part in a ground-breaking ceremony marking the start of construction at a new Royal Navy base at Mina Salman Port, which will allow longer-term deployments in the Gulf.
In an interview with the BBC, Mr Hammond also said the UK needed to show more of a "duty of care" to vulnerable people at risk of being radicalised by extremists.
Asked by BBC security correspondent Frank Gardner if the new counter-extremism strategy was an admission of failure, not just by this government but by previous governments, Mr Hammond said: "I don't think it's just a failure by governments, I think it's a question about how our society has dealt with these issues in the past.
"And the doctrine of multiculturalism that we clung to for a long time in the UK, I'm afraid, encouraged us to turn a blind eye to things that we should have addressed.
"It allowed us to overlook intolerance that was going on under our very noses."
He said the new strategy was intended to tackle that.
"We can no longer allow the consequences of that, in terms of radicalisation of young men and women in Britain, many of whom have gone to Iraq and Syria to fight, some of whom have died there," said Mr Hammond.
"So we have to be more mindful of a duty of care to counter extremist agendas, to intervene, to protect vulnerable people from being radicalised."
Referring to the Trojan Horse affair, during which it was claimed some conservative Muslim groups were attempting to take control of a number of schools in Birmingham, he added: "We've had to learn from this about what's going on in our schools, our prisons, our mosques, our internet and make sure we address it."


Vote Leave says the UK government will pay Albania, Macedonia, Montenegro, Serbia and Turkey a total of £1.2bn between 2014 and 2020 as part of the EU fund to help these countries to join the EU.

The Claim: Vote Leave says the UK will be obliged to pay £1.8bn by 2020 to encourage Albania, Macedonia, Montenegro, Serbia and Turkey to join the EU.
Reality check verdict: Over a seven year period, £1.2bn of the UK's contributions to the EU Budget will go to seven candidate states. The UK committed another £250m towards helping Turkey support Syrian refugees for two years and might commit more in the future.
They say that the UK will pay Turkey a further £640m "as part of the recent EU-Turkey deal designed to facilitate Turkish accession to the EU", bringing the total to £1.84bn.
In 2014 the EU agreed to use a total of €11.7bn (£9.1bn) from its seven-year budget 2014-2020 to help seven EU candidate countries - Albania, Macedonia, Montenegro, Serbia, Turkey, Bosnia and Herzegovina and Kosovo - make political and economic reforms.
Turkey, the largest of the seven countries, will receive a total of €4.5bn over the seven year period. Albania will receive €649m.
On the basis of the 2014-2020 EU fund, Vote Leave calculated the UK's share of the total the EU is spending on reforms in those seven countries.
The UK's contribution to the EU Budget varies from year to year. It has been around 12% to 13% of the total in recent years and the Treasury says it was 12.57% in 2015. Vote Leave used the UK's 2015 share of the total and 2014 exchange rates and arrived at the figure of £1.2bn as the UK contribution to the programme.
Of the seven countries helped by this EU fund, Turkey has progressed furthest in its pursuit of EU membership, but it is nevertheless unlikely to join in the next 10 years.
The second part of this claim, that the EU recently agreed a deal with Turkey "to facilitate Turkish accession to the EU" is incorrect.
The EU and Turkey signed a deal in November 2015 to support Syrian refugees in Turkey in an attempt to reduce the number of refugees crossing into Greece. The EU will provide €3bn over the next two years for this programme, €1bn of which will come from the EU budget and the rest from contributions from member states according to the size of their economies.
Germany, which has the biggest economy, will pay €428m, while the UK will pay €328m (£250m).
The UK's contribution will count towards the UK's aid target of 0.7% of national income.
In addition, the EU promised an extra €3bn for Turkey by 2018 if the first programme for supporting Syrian refugees is successfully completed. There is no detail on whether this would come out of the EU Budget or be met by bilateral contributions.
Read more: The facts behind claims in the EU debate


Motherwell have signed striker Alex Fisher and midfielder Gael Bigirimana on two-year contracts.

Fisher joins following his departure from Inverness Caledonian Thistle, while Bigirimana makes the switch from Coventry City.
Their arrival coincides with the departure from Fir Park of assistant manager James McFadden.
The 34-year-old's contract has expired and manager Stephen Robinson has decided to change his backroom set-up.
"James and I have worked together over the last few months, but I feel something a bit different will be beneficial to the squad," said Robinson.
"It's a tough call because James is a top lad and he's done so much for the club.
"We both had a good, open and honest chat after the game at Inverness. James is at the start of his coaching pathway, still doing his badges and qualifications, and I have no doubt he will make a very good manager one day. We've left each other on good terms."
McFadden, who scored his 44th goal for the club at Inverness on the final day of the season, said he would "take the summer to weigh everything up".
In terms of the new arrivals, Fisher, 26, scored six goals in the final six games of the 2016-17 season but could not save ICT from relegation.
Burundi international Bigirimana, 23, was on loan at Rangers from Newcastle in 2015 but did not play a match.
Robinson said of Fisher: "He will add a bit of firepower to the side. There's a variation in his goals as well, so we've got ourselves a terrific first signing."
The 6ft 3in target man joined Caley Thistle in January 2016 only to suffer a season-ending injury after three outings as a substitute.
This term he managed a total of eight goals from 25 appearances.
Having played in the lower leagues of Spain, Belgium and Italy, he moved to Scotland from Torquay United.
Speaking to MFC TV, Fisher said: "It's fantastic, I spoke to the gaffer at the end of the season, had a good talk and I'm delighted to get this move over the line.
"It's a big club with a great fan base and good history, and when I spoke to the manager and he told me about his plans for this season I knew I wanted to be a part of it so it was an easy decision."
Bigirimana started his career at Coventry before being bought by Newcastle for a fee of between £500,000 and £1m in 2012. He was loaned back to Coventry before making a permanent switch to the club in the summer of 2016.
Find all the latest football transfers on our dedicated page.


Venezuela's military has taken control of five ports in an effort to guarantee supplies of food and medicine.

In a decree, President Nicolas Maduro has ordered the army to monitor food processing plants, and co-ordinate the production and distribution of items.
Venezuela is going through a deep economic crisis despite having the world's largest oil reserves.
Basic products are increasingly hard to find and many say they struggle to feed their families.
The Venezuelan Bishops Conference said the rise of the military is a "threat to tranquillity and peace".
Mr Maduro says the measure is to fight the "economic war" he claims is being waged against his government by political foes and businessmen, with US backing.
But the opposition says the government has mismanaged the economy, and has called for a referendum to oust the president.
Venezuela: Economy on the brink?
Mr Maduro announced on state television that the ports of Guanta, La Guaira, Puerto Cabello, Maracaibo and Guamache would be controlled by the army.
He created a government initiative called Great Mission of Sovereign Supplying, which will be headed by the country's Defence Minister, General Vladimir Padrino.
Among other things, it can establish how purchases and distribution of food, medicine and household goods are made.
Meanwhile, Mr Maduro accused Citibank of mounting a "financial blockade" on the country, after the US bank decided to close the government's international payments account with it.
Citibank said the decision followed a "periodic risk management review", but did not explain further. It would be implemented within 30 days, it added.
Due to strict currency controls in place since 2003, the Venezuelan government relies on Citibank for foreign currency transactions.


The UK gambling industry is betting on a wave of mergers and acquisitions to secure a more profitable future.

A raft of big deals this year include the £2.3bn tie-up between Ladbrokes and Gala Coral in July, a £6bn merger of Betfair and Paddy Power in August, and GVC's £1.1bn ($1.5bn) acquisition of Bwin.party in September.
Analysts say a "mergers and acquisitions frenzy" is sweeping the UK.
In fact, in the year to August, there were more takeovers and mergers in the UK gambling sector than in any other country.
According to Nick Batram, an analyst at brokerage Peel Hunt, operators are looking to scale up for two main reasons.
He says:  "On the one hand they are seeing the costs of tax, compliance and technology go up, and want to offset this.
"But they are also looking for new ways to grow as the market becomes more competitive."
At first glance this may seem odd. According to the Gambling Commission, revenue in the UK gambling industry climbed from £5.6bn in 2010 to £7.1bn in 2014.
But this disguises the fact that almost all of the growth happened online, with consumers increasingly opting to gamble on mobile devices.
As a result, High Street operators face tough trading conditions - a situation worsened by an increasingly challenging regulatory environment, which includes a maximum betting tariff of £50 each time on gaming machines.
Mr Batram says: "You have new restrictions placed on people who want to stake more than £50 a spin on machines.
"Furthermore, machine gaming duties now stand at up to 25%.
"And buying land-based assets is quite expensive anyway, because you have bricks and mortar."
High Street bookmakers Ladbrokes and Gala Coral joined forces this summer in a bid to offset these pressures. The deal will create the UK's largest bookmaker, with around 4,000 high street betting shops, resulting in a predicted £65m of cost efficiencies.
"Ladbrokes has pretty much been running the same business as Coral, but with a different colour and a different brand, " explains Paul Leyland from Regulus Partners, an advisory business that focuses on the gambling sector.
He adds: "[And] recently Coral has been doing it much better."
Mr Leyland says that if the two firms can eliminate duplication costs and stick with the "best breed of management", they will be in a stronger position to grow.
He also says the combined group needs to invest more in its mobile offering, and boost the overall user experience.
Paddy Power, a familiar High Street and online betting shop, used it's 2014 annual report to claim that "over 90% of future growth would be in mobile".
And so its agreement this summer to combine with website betting exchange Betfair - making them one of the world's biggest online gaming firms - came as little surprise.
Yet despite Paddy Power's optimistic forecast, the online gambling space is becoming more challenging as countries around the world update their regulations.
For the online gambling sector, this has resulted in higher compliancy costs and taxes.
Mark Jordan, a partner at accountancy group PWC, highlights the UK's crackdown on gambling websites which have their headquarters in Gibraltar, such as Ladbrokes' online offering, Bet Victor and Stan James.
He says: "Previously if I was headquartered in Gibraltar offering online betting to someone in the UK, that would be tax free, whereas now there is a point of consumption tax which is levied by HMRC at 15%."
Mr Batram says such pressures make it harder to invest in the technology underpinning a product.
"It's risky given how low the barriers to entry are in online gaming - providers have suddenly realised this comes off their margins, and so you're looking into consolidation and cost savings at scale again."
Mr Batram adds: "Gone are the days when you could just sling up an online casino and watch the money roll in.
"The online market is much more competitive, so your site has to feel right, look right and that costs money."
Mr Jordan says that private equity companies - which were all but absent from the gambling sector five years ago - are also driving consolidation.
He points to last December's announcement that Luxembourg-based private equity group CVC Capital Partners was buying a 80% stake in Sky Bet.
And this month online betting firm Bwin accepted a £1.3bn takeover offer from fellow private equity firm GVC Holdings.
GVC Holdings, which already owns Sportingbet, outbid rival bidder, gambling business 888 Holdings.
Mr Jordan says: "Private equity firms like to find a business with potential, build it up and then merge it with something else, so they're having a big influence on the market."
Most analysts expect that consolidation in the gambling sector will only continue as the years progress, with larger conglomerates coming to dominate the industry.
Such firms are said to be better placed to handle regulatory and tax pressures.
However, Mr Jordan also expects to see a "small hardcore of [small] online gaming companies survive, which may not adhere to regulation, or which pick markets where they don't have the same rules".
And Mr Leyland says that small and specialist gambling companies, focused on niche markets or new products, will also thrive.
He adds: "The big risk is for medium-sized firms with a lot of money, invested in doing exactly the same thing as all their competitors."
With firms like Paddy Power betting on a digital future, it seems that companies focused on the High Street are most at risk.
But Mr Batram says it would be wrong to write them off just yet: "I think land-based gambling can still offer value if done right, and there's a lot of talk about retail combining with digital to create more touch-points for consumers.
Just as online hasn't killed cinema or high street shopping, I think it will remain an important part of the mix."


Weight Watchers International is reportedly a takeover target for an unnamed activist hedge fund.

Few details were available, but media reports were enough to send shares in Weight Watchers up around 16%.
The share price  has tumbled 85% this year on losses and criticism that it has been too slow to react to competition and new health trends.
The New York-based firm, which could be valued at about $2bn (Â£1.3bn), saw profit fall 52% last year.
The hedge fund has reportedly bought Weight Watchers loans, due for repayment in April next year, and is now talking to potential partners about a possible joint bid.
The company is still the world's leading weight loss brand, but fewer people have been subscribing to classes, with mobile apps and activity monitors a contributing cause.
In the US, where the company has the majority of its subscribers, the number of people signing up has fallen by more than 20%.


A group of Iranian fans who created a tribute to Pharrell Williams' hit song Happy have been arrested.

The video shows three men and three unveiled women dancing to the song on the streets and rooftops of Tehran.
Police chief Hossein Sajedinia said the "vulgar clip" had "hurt public chastity", the ISNA news agency said.
Iran's state-run TV broadcast a programme on Tuesday, apparently showing the men and women confessing on camera.
A subtitled edition of the TV clip, posted on YouTube, identified the detainees as "actors" who claimed they were tricked into making the Happy video for an audition.
By Ali HamedaniBBC Persian
The young people in the video are students, film-makers and photographers.
Their video appeared during the Persian New Year, at the end of March, and it was an instant hit on Iranian social media sites, inspiring several copies.
It is just the latest example of young Iranians using the internet to challenge the restrictions on their everyday lives.
In the past month, hundreds of Iranian women have been defying the rules requiring them to cover their heads in public, by sending photographs of themselves without headscarves, to a newly created Facebook site called "My Stealthy Freedom".
Arash Sobhani, leader singer of the Iranian underground rock group Kiosk, who now lives in the US told BBC Persian that the Iranian authorities continuing attempts to crackdown on "un-Islamic" behaviour were not working.
"They banned our music, broke our guitars, attacked our parties and stopped our concerts," he said. "But did we stop? No!"
"They told me they are making a feature film and they had a permit for it," said one man in the video. "They said those things and they fooled me."
Another young woman added: "They had promised us not to publish the video."
According to some unconfirmed reports, a total of 13 people were arrested in connection with the video, but official sources have not confirmed the exact number of detainees.
Williams, whose song was nominated for an Oscar earlier this year, has protested at the arrests.
"It is beyond sad that these kids were arrested for trying to spread happiness," the singer wrote on his Facebook page.
Iran's president Hassan Rouhani also appeared to criticise the arrest.
A unofficial twitter account, widely believed to be associated with the President, posted a comment he first made last year, saying: "#Happiness is our people's right. We shouldn't be too hard on behaviours caused by joy."
Under Iran's interpretation of Islamic law, women must cover their hair and wear loose-fitting clothing meant to preserve their modesty.
Patrols of so-called "morality police" regularly enforce standards of Islamic dress on Iran's streets. However, the rules are widely flouted.
The internet is also heavily filtered in Iran, with the authorities blocking access to popular social networking sites.
The "Happy we are from Tehran" video, originally posted in March, has now been seen more than 40,000 times.
At the end of the clip, the credits read: "Happy was an excuse to be happy. We enjoyed every second of making it. Hope it puts a smile on your face."
Iranian journalist Golnaz Esfandiari tweeted in response to the arrests: "Iran [is] a country where being 'happy' is a crime.
"Thousands of Iranians have been arrested in the past 35 years for being happy [and] partying."
Arash Sobhani, leader singer of the Iranian underground rock group Kiosk, told the BBC's Persian service that attempts to suppress musicians were not working.
"They banned our music, broke our guitars, attacked our parties and stopped our concerts," he said. "But did we stop? No!"
Many Twitter users have begun using the hashtag #freehappyiranians to put pressure on the Iranian authorities to release those arrested over the video.
Williams' song has inspired hundreds of tributes since it was released last year on the soundtrack to hit animation Despicable Me 2.
The music video lasted an exhausting 24 hours - with dozens of people filmed lip-syncing and dancing to the feel-good anthem, which was played on a loop.
The clip sparked a YouTube craze, with thousands fans around the world staging their own performances of the song.
When shown a montage of the tributes on the Oprah Winfrey show last month, Williams began to cry, saying the response to the song had been "overwhelming".
In the UK, the track has reached number one on three separate occasions, while in the US it spent 10 weeks at the top of the Hot 100.


1842 - China cedes Hong Kong island to Britain after the First Opium War. Over the decades, thousands of Chinese migrants fleeing domestic upheavals settle in the colony.
1898 - China leases the New Territories together with 235 islands to Britain for 99 years from 1 July.
1937 - With the outbreak of the Sino-Japanese War, Hong Kong becomes a refuge for thousands of mainland Chinese fleeing before the advancing Japanese.
1941 - Japan occupies Hong Kong. Food shortages impel many residents to flee to mainland China. The population drops from 1.6m in 1941 to 650,000 by the end of the Second World War.
1946 - Britain re-establishes civil government. Hundreds of thousands of former residents return, to be joined over next few years by refugees fleeing the civil war between the Nationalists and the Communists in China.
1950s - Hong Kong enjoys economic revival based on light industries such as textiles.
1960s - Social discontent and labour disputes become rife among poorly-paid workforce.
1967 - Severe riots break out, mainly instigated by followers of China's Cultural Revolution.
Late 1960s - Living conditions improve and social unrest subsides.
1970s - Hong Kong is established as an "Asian Tiger" - one of the region's economic powerhouses - with a thriving economy based on high-technology industries.
1982 - Britain and China begin talks on the future of Hong Kong.
1984 - Britain and China sign Joint Declaration on the conditions under which Hong Kong will revert to Chinese rule in 1997. Under the "one country, two systems" formula, Hong Kong will become part of one communist-led country but retain its capitalist economic system and partially democratic political system for 50 years after the handover.
1989 - The massacre of pro-democracy demonstrators in Beijing's Tiananmen Square leads to calls for the introduction of further democratic safeguards in Hong Kong.
1990 - Beijing formally ratifies Hong Kong's post-handover mini-constitution or Basic Law.
1992 April - Chris Patten becomes last British governor of Hong Kong, with a brief to oversee the colony's handover to China.
1992 October - Chris Patten announces proposals for the democratic reform of Hong Kong's institutions aimed at broadening the voting base in elections. China is outraged that it has not been consulted and threatens to tear up business contracts and overturn the reforms after it has taken control.
1992 December - Hong Kong stock market crashes.
1994 June - After nearly two years of bitter wrangling, Hong Kong's legislature introduces a stripped-down version of Chris Patten's democratic reform package. The new legislation widens the franchise but falls far short of providing for universal suffrage.
1995 - Elections held for new Legislative Council (LegCo).
1997 July - Hong Kong is handed back to the Chinese authorities after more than 150 years of British control. Tung Chee-hwa, a Shanghai-born former shipping tycoon with no political experience, is hand-picked by Beijing to rule the territory following the takeover.
1998 May - First post-handover elections held.
2001 February - Deputy Chief Executive Anson Chan, a former deputy to Chris Patten and one of the main figures in the Hong Kong administration to oppose Chinese interference in the territory's affairs, resigns under pressure from Beijing and is replaced by Donald Tsang.
2002 June - Trial of 16 members of the Falun Gong spiritual movement arrested during a protest outside Beijing's liaison office in the territory. Falun Gong remains legal in Hong Kong, despite having been banned in mainland China in 1999, and the trial is seen as a test of the freedoms Beijing guaranteed to respect after the handover. The 16 are found guilty of causing a public obstruction.
2002 September - Tung Chee-hwa's administration releases proposals for controversial new anti-subversion law known as Article 23.
2003 March-April - Both China and Hong Kong are hit by the pneumonia-like Sars virus. Strict quarantine measures are enforced to stop the disease spreading. Hong Kong is declared free of Sars in June.
2003 July - A day after a visit to the territory by Chinese Premier Wen Jiabao, 500,000 people march against Article 23. Two Hong Kong government members resign. The bill is shelved indefinitely.
2004 April - China rules that its approval must be sought for any changes to Hong Kong's election laws, giving Beijing the right to veto any moves towards more democracy, such as direct elections for the territory's chief executive.
2004 July - Some 200,000 people mark the seventh anniversary of Hong Kong's handover to Chinese rule by taking part in a demonstration protesting Beijing's ruling against electing the next chief executive by universal suffrage.
Britain accuses China of interfering in Hong Kong's constitutional reform process in a manner inconsistent with self-governance guarantees agreed before the handover.
2004 September - Pro-Beijing parties retain their majority in LegCo elections widely seen as a referendum on Hong Kong's aspirations for greater democracy. In the run-up to the poll, human rights groups accuse Beijing of creating a "climate of fear" aimed at skewing the result.
2004 December - Chinese President Hu Jintao delivers public rebuke to Tung Chee-hwa, telling him to improve his administration's performance.
2005 March - Amid mounting criticism of his rule, Tung Chee-hwa resigns, citing failing health. He is succeeded in June by Donald Tsang.
2005 May - Hong Kong's highest court overturns the convictions of eight of the Falun Gong members who were found guilty of causing an obstruction in the territory in 2002.
2005 June - Tens of thousands of people commemorate sixteenth anniversary of crackdown on pro-democracy demonstrations in Tiananmen Square. Hong Kong is the only part of China where the 1989 events are marked.
2005 September - Pro-democracy members of LegCo make unprecented visit to Chinese mainland. Eleven members of the 25-strong pro-democracy group had been banned from the mainland for 16 years.
2005 December - Pro-democracy legislators block Mr Tsang's plans for limited constitutional reforms, saying they do not go far enough. Mr Tsang said his plans - which would have changed electoral processes without introducing universal suffrage - went as far as Beijing would allow.
2006 March - Pope Benedict XVI elevates Bishop Joseph Zen, the leader of Hong Kong's 300,000 Catholics and an outspoken advocate of democracy, to the post of cardinal. China warns Cardinal Zen to stay out of politics.
2006 July - Tens of thousands of people rally in support of full democracy.
2007 January - New rules aim to restrict the number of pregnant women from mainland China who come to Hong Kong to give birth. Many had been drawn by the prospect of gaining Hong Kong residency rights for their children and evading China's one-child policy.
2007 April - Chief Executive Donald Tsang is appointed to a new five-year term after winning elections in March.
2007 July - Hong Kong marks 10th anniversary of handover to China. New government under Chief Executive Donald Tsang is sworn in. Plans for full democracy unveiled.
2007 December - Beijing says it will allow the people of Hong Kong to directly elect their own leader in 2017 and their legislators by 2020. Mr Tsang hails this as "a timetable for obtaining universal suffrage", but pro-democracy campaigners express disappointment at the protracted timescale.
2008 September - Hong Kong's pro-democracy camp wins more than a third of seats in legislative elections, retaining a key veto over future bills.
2009 June - Tens of thousands of people attend a vigil in Hong Kong on the 20th anniversary of the Tiananmen Square massacre. The territory is the only part of China to mark the anniversary.
2009 December - Hong Kong authorities unveil proposals for political reform in response to pressure for greater democracy, including an enlarged Legislative Council; critics say the moves do not go far enough.
2010 May - Five opposition MPs are returned to their seats, in by-elections they triggered by quitting - a move intended to pressure China to grant the territory full democracy.
Opposition Democratic Party, traditionally hostile to Beijing, holds its first talks with a Chinese official since the 1997 handover.
2012 July - Leung Chun-ying takes office as chief executive, succeeding Donald Tsang whose last months in office were dogged by controversy over his links with wealthy businessmen.
2012 September - Pro-democracy parties retain their power of veto over new laws in Legislative Council elections, but perform less well than expected. Turnout, at over 50%, was higher than in 2008.
2013 June - Hundreds march in support of whistleblower Edward Snowden, who fled to Hong Kong after exposing secret US surveillance programmes.
2014 June - More than 90% of the nearly 800,000 people taking part in an unofficial referendum vote in favour of giving the public a say in short-listing candidates for future elections of the territory's chief executive. Beijing condemns the vote as illegal.
2014 July - Tens of thousands of protesters take part in what organisers say could be Hong Kong's largest pro-democracy rally in a decade.
2014 August - Chinese government rules out a fully democratic election for Hong Kong leader in 2017, saying that only candidates approved by Beijing will be allowed to run.
2014 September-November - Pro-democracy demonstrators occupy the city centre for weeks in protest at the Chinese government's decision to limit voters' choices in the 2017 Hong Kong leadership election. More than 100,000 people took to the streets at the height of the Occupy Central protests.
2014 December - Authorities take down Mong Kok protest camp, leaving a few hundred protesters at two camps at Admiralty and Causeway Bay.
2014 December - Hong Kong tycoon and former government official Thomas Kwok is sentenced to five years in jail in the city's biggest-ever corruption case.
2015 June - Legislative Council rejects proposals for electing the territory's next leader in 2017. Despite pro-democracy protests and a lengthy consultation process, the plans remained the same as those outlined by China in 2014.
2016 August - Hundreds of protesters rally against the disqualification of six pro-independence candidates from Legislative Council elections on 4 September.
2016 September - A new generation of pro-independence activists win seats in Legislative Council elections in the highest turnout since the 1997 handover from Britain to China.
2016 November - Thousands of people gather in central Hong Kong to show their support for China's intervention in the territory's political affairs after Beijing moves to have two pro-independence legislators removed from office.
2016 November -The high court disqualifies pro-independence legislators Sixtus Leung and Yau Wai-Ching from taking their seats in the Legislative Council after they refused to pledge allegiance to China during a swearing in ceremony.
2016 December - Chief Executive CY Leung announces he will not see re-election when his current term ends in July 2017, citing family reasons.
2017 February - Former chief executive Donald Tsang is sentenced to 20 months in prison for misconduct in public office after he was accused of concealing private rental negotiations with a property tycoon for a luxury apartment in China, in return for awarding its owner a broadcasting licence.


Three little spots on a cracked smartphone screen show Brent Stapelkamp the last known locations of Jericho the lion.

Every two hours his tracking collar pings the satellite and it's clear on the map that the lion, who was Cecil's buddy, has left the protection of Hwange National Park and ventured onto private hunting land.
It's the same place where Cecil was killed and Jericho, who led the pride with him, has spent a lot of time there recently - calling for his friend.
Brent, who is a field researcher with Oxford University's Wildlife Conservation Research Unit, had been following Cecil for nine years and it was he who discovered the lion had been killed.
"When he's walking it's a long line of dots on the map, but if he's been eating something it's in a big cluster," he said.
"The fact he had been eating before his collar switched off gave me that sense that he had been on a bait."
The last known position was enough to lead the authorities to Cecil's remains.
A railway line is all that divides the park from private hunting land. There's no fence or barrier and as we watched, animals were coming and going easily across the track.
The professional hunter who led Walter Palmer's now infamous expedition is on trial - and the man who owns the land may face charges of allowing a lion to be killed without a permit.
Hunting some of the big game animals, including lions, has been suspended around Hwange, while the quota system is investigated.
This, along with the international outcry, means Jericho is safe for now.
His cubs also seem to be alive and well. Just before dawn two females and their young crossed the road ahead of us, close to the area that had been Cecil's territory.
The international reaction to the killing of the famous lion has sparked fierce debate over whether "trophy hunting" should be banned.
But there's little debate here, even among conservationists.
Cecil the lion: In pictures
When is hunting not poaching?
Brent Stapelkamp's position is not surprising: "Personally I don't want to see lion hunting ever again - just because of the way lions react to it."
But he doesn't want it banned.
"Hunting can be a valuable component to conservation. If a property has a hunting quota and that money comes back from hunting into the management of the land, it's not going to be at risk," he said.
"So we have to be careful. The world reaction might polarise things and hunting might be banned outright.
"I think we have to be very cautious about how this momentum can be used."
Protected animals cannot be killed.  For the others, hunting quotas are set - typically at 0.5-2% of the population in any given area.
If the system works properly the money is used to fund the national park, to pay rangers and protect animals.
Trevor Lane from the Bhejane Trust conservation group says there is a far greater threat to the land from poaching.
This can either be from commercial poaching for elephant tusks or rhino horns - or subsistence poaching by impoverished local people snaring a deer to eat, but killing big game as well.
"If we took the hunting out of those areas without offering an alternative, they would be poached out within two years. There would be nothing left," he said.
"The hunting brings in revenue. I know it's a terrible thing to some people, but we have to be practical and we have to be realistic here.
"Whether we lose a few animals, which pays for the conservation, or whether we lose the whole lot is the option faced in many areas.
"We just don't have the finance or the ability to look after those areas. If there was an alternative I'm sure everyone would look at it."
Many here hope the outcome of the investigation and the attention to the system will mean better protection for the animals, but it all comes down to funding.
"There's a general agreement our current regulations and statues suffice, but maybe we have to do more in terms of monitoring and enforcement," said Edison Chidziya, director general of Zimbabwe National Parks and Wildlife Management.
The global focus on Cecil has brought the whole industry together. There is optimism it will tighten regulations and squeeze those who have been breaking the law.
But by focusing on trophy hunters above all else, public opinion is perhaps missing a bigger point.
Poaching is driving many species towards extinction and there are other parts of the hunting industry here and across Africa that would benefit from closer scrutiny.


England defender Luke Shaw has joined Manchester United from Southampton for £27m, making him one of the world's most expensive teenagers.

The 18-year-old's fee could rise to £31m, depending on his performance. An initial £27m offer was rejected in May.
He has developed immensely during his time at Southampton and has all the attributes to become a top player
The left-back has agreed a four-year contract with United, with an option to extend for a further year.
"I want to continue to progress my career and joining United is the ideal place for me to do that," he said.
Ryan Giggs, United's assistant manager, added: "Luke is a very talented young left back with great potential.
"He has developed immensely during his time at Southampton and has all the attributes to become a top player."
Shaw told Saints at the end of last season that he wanted to join United.
He became the youngest player to feature at the 2014 Fifa World Cup in Brazil when he played the entire 90 minutes of England's 0-0 draw with Costa Rica on Tuesday.
He is United's second summer recruit - and second in as many days - after they signed Spain midfielder Ander Herrera, 24, from Athletic Bilbao for a fee believed to be £29m.
Manchester United's Wayne Rooney was the world's most expensive teenager when he moved to Old Trafford in September 2004 for an initial fee of £20m.
Shaw's signing eclipses that and matches the £27m Paris St-Germain paid Roma for 19-year-old Marquinhos in July.
The youngster also becomes the fourth most expensive defender in world football.
Southampton insist the money they have received from United will be reinvested in the team.
"While we are sad to see Luke depart the club, we fought to ensure that we got the right deal for a player in whom we have invested a great deal of work over the past decade," said executive director Les Reed.
"This deal is a good one for Southampton Football Club and hopefully sends a clear message to other clubs wishing to bid for our players.
"Luke's transfer fee will be reinvested into the team as our new manager, Ronald Koeman, builds for the new season and for years to come."
Meanwhile, Saints midfielder Adam Lallana is set to have a medical ahead of a proposed £25m move to Liverpool.
The 26-year-old England international is expected to complete his transfer within the next 24 hours.
England striker Rickie Lambert has already moved from Saints to Anfield.


Hundreds of people have attended the funeral of a a mentally ill black man in Ottawa who died following a confrontation with Canadian police.

Ottawa Mayor Jim Watson was among those who came to pay last tributes to Abdirahman Abdi at a city mosque.
Mr Abdi, 37, a Somali immigrant, died on Monday, a day after being arrested for allegedly fondling a woman.
A video has emerged showing him bleeding and handcuffed during the arrest. The case is being investigated.
In a statement, Mr Abdi's family said he was a "wonderful son, amazing brother and kind-hearted uncle".
The family said that "what happened to him that Sunday wasn't fair at all and shouldn't be justified by any means" and "we all have many questions".
He arrived in Canada in 2009, according to his brother Abdiaziz.
The circumstances of Mr Abdi's death are now being investigated by Ontario's Special Investigation Unit.
The case has sparked a debate about race relations in Canada - a nation that is widely seen as being tolerant.
Ottawa's police chief Charles Bordeleau said on Friday that there had been "a number of incidents" involving his officers, including taunts, since the death of Mr Abdi.


Tom Shanklin would like to see Luke Charteris move back to Wales if the Wales lock leaves French club Racing 92 at the end of the season.

Charteris, 32, is in talks with English Premier side Bath about a potential move when he is out of contract.
But former Wales centre Shanklin hopes the ex-Newport Gwent Dragon might yet decide to come home to Wales.
"If we want the regions to play better, we need the best players playing there," Shanklin said.
"That will improve the whole league. It would be great to see him back at a Welsh region.
"Ideally we'd like to see him in a region, but if it's Bath I'm sure Wales will be able to control him slightly better being in Bath.
"I'm not writing him off, but he is at that age now that he'll maybe want to experience something new.
"He's done the Welsh thing, he's done the French thing, this is a new challenge for him."
Dragons are keen to take back their former player Charteris, who left them to join Perpignan in 2012, but coach Kingsley Jones has said they will probably be unable to match the likes of Bath financially.
But with Wales and British and Irish Lions centre Jonathan Davies returning to Scarlets from Clermont Auvergne next season, Shanklin is hopeful the tide of Welsh player departures has turned.
Shanklin won 70 Wales caps before a knee injury forced him to retire in 2011.
He told BBC Radio Wales: "We have heard some good news in Jon Davies coming back, there's rumours of Leigh Halfpenny, of George North.
"If we want to improve the Pro12 and get the quality and the intensity that we see in Europe, we need out best players back."


The Australian authorities could have prevented the rape and murder of Irish woman Jill Meagher by revoking her killer's parole as soon as he breached it, a coroner has found.

No inquest has been held into the 2012 murder at her family's request.
Ms Meagher was originally from Drogheda, but moved to Australia from Ireland in 2009 with her husband.
She worked for ABC Radio but went missing during a night out with colleagues.
Her body was discovered six days later buried on the outskirts of Melbourne.
Adrian Bayley, who had a history of violent sex attacks, was sentenced to life imprisonment with a minimum jail term of 35 years for her murder.
On Friday, coroner Ian Gray said Jill Meagher's death had been "preventable".
He pointed to failings by Community Correctional Services (CCS), a division of Corrections Victoria and the Adult Parole Board (APB), a separate body within the Department of Human services.
"A more rigorous, risk-averse approach by CCS and the APB would have led to a cancellation of Bayley's parole," Mr Gray said.
"The approach taken is difficult to understand ... it did not bring dangerous and high risk parolees immediately to account."
Bayley had been on parole for previous rapes when he raped and murdered Ms Meagher as she walked home from Brunswick in the early hours of 22 September 2012.
He was also on bail pending an appeal of a three-month sentence after pleading guilty to attacking a man outside a pub at Geelong in 2011.
At the time of that incident, Bayley had been on parole after serving eight years' jail for 16 counts of rape against five women.
He had already served time for rapes committed from the age of 18.
The coroner noted Victoria's parole system had been amended since Ms Meagher's murder.
Had it been changed when Bayley was charged with the Geelong assault, a representative from Corrections Victoria told the coroner, his parole probably would have been cancelled automatically when he was convicted of that offence.
"The poignant truth of this ... will resonate with Ms Meagher's husband, family and friends," the coroner said.


Reading midfielder Liam Kelly has signed a new three-year contract with the club following an impressive first full season in the senior side.

He made 36 appearances last season, including as a substitute in the Championship play-off final.
Kelly, 21, has been with Reading since the age of eight.
"He took first-team football in his stride last season and certainly deserves this new contract," chief executive Nigel Howe said.


An incredibly eventful last 10 minutes saw Dover secure a 4-2 win at Eastleigh.

After a goalless first half, Ryan Huddart's own-goal gave Dover the lead on 52 minutes, before Ross Lafayette doubled the advantage against his former club on the hour-mark.
Ryan Bird pulled one back for the Spitfires on 81 minutes, but that was just the start of the late action. Five minutes later, it looked like the hosts had rescued an unlikely point when Andy Drury poked home the rebound following Adam Dugdale's long-range effort.
Just a minute later the game turned again thanks to Jim Stevenson's strike, and there was still time for Dover striker Ricky Miller to make sure of the win.
Report supplied by the Press Association.
Match ends, Eastleigh 2, Dover Athletic 4.
Second Half ends, Eastleigh 2, Dover Athletic 4.
Goal!  Eastleigh 2, Dover Athletic 4. Ricky Miller (Dover Athletic).
Goal!  Eastleigh 2, Dover Athletic 3. Jim Stevenson (Dover Athletic).
Goal!  Eastleigh 2, Dover Athletic 2. Andy Drury (Eastleigh).
Goal!  Eastleigh 1, Dover Athletic 2. Ryan Bird (Eastleigh).
Substitution, Dover Athletic. Ricky Miller replaces Moses Emmanuel.
Substitution, Eastleigh. Ryan Bird replaces Jason Taylor.
Substitution, Eastleigh. Scott Wilson replaces Yemi Odubade.
Goal!  Eastleigh 0, Dover Athletic 2. Ross Lafayette (Dover Athletic).
Own Goal by Ryan Huddart, Eastleigh.  Eastleigh 0, Dover Athletic 1.
Substitution, Eastleigh. Jai Reason replaces David Pipe.
Second Half begins Eastleigh 0, Dover Athletic 0.
First Half ends, Eastleigh 0, Dover Athletic 0.
Adam Dugdale (Eastleigh) is shown the yellow card for a bad foul.
First Half begins.
Lineups are announced and players are warming up.


A World War One soldier's account of sharing "cigs, jam and corn beef" with Germans during the Christmas truce has been revealed in a collection of letters.

Frederick James Davies, of Lampeter, Ceredigion, described meeting enemy soldiers across No Man's Land on 25 December 1914.
The details were in a letter written to his mother from the front line.
He said they had a "good chat with the Germans on Xmas day".
Soldiers serving in northern France left their trenches along some parts of the Western Front on the first Christmas Day of the conflict to meet the enemy and exchange gifts.
Some are famously said to have played football.
Mr Davies, a private in the 2nd Battalion Royal Welsh Fusiliers, described the brief armistice in correspondence among the collection found by his granddaughter, Jane Oliver.
"They (the German soldiers) were only 50 yards (45m) away from us in the trenches. They came out and we went to meet them," he wrote.
"We shook hands with them. We gave them cigs, jam and corn beef.
"They also gave us cigars but they didn't have much food. I think they are hard up for it. They were fed up with the war."
In the same letter, he described how they had come out of trenches for a few days of rest, commenting that it was nice to sleep away from the wet, although they were still sleeping in their clothes.
"I am happy through it all. It's no use being otherwise," he said.
Mr Davies, who was born in 1886 and joined the army in 1908, also sent home pressed flowers to his mother.
He left the army in 1915 after a trench caved in on him, shattering his spine and leaving him unable to work properly.
He married in 1919 and had three children.
His youngest daughter, Audrey Trenchard, now 86, said he never spoke about his war experiences before his death, aged 61, and "it was so interesting" to read the letters.
"We were so thrilled that Jane had managed to find them and keep them," she said.
"I didn't know about it, being the youngest I hadn't heard any of this. It's wonderful for me to find out about it."
Mrs Trenchard said her father's letters were an "important" reminder "that the Germans weren't all bad".
"They were family men, like ours were," she added.


Nearly a quarter of Asian voters do not know which party they will support at the general election, a BBC survey suggests.

The BBC Asian Network/ICM poll of 500 people also found that, of those who had decided, 39% said they may change their minds before 7 May.
It shows the Asian vote in Britain, traditionally considered to lean towards Labour, is still up for grabs.
Half of those questioned said they wanted tougher immigration controls.
The poll questioned 500 people across England, Scotland and Wales who described themselves as Asian between 25 March and 2 April.
The poll found that 24% of respondents were still undecided about which party to vote for - in line with the population as a whole.
There has been much interest in the "Asian vote" since the 2010 general election - when Labour secured 68% of ethnic minority votes.
The Conservatives, on the other hand, managed 16%.
Since then, several studies have suggested the ethnic minority vote could play a significant role in key marginal seats.
Dr Alexandra Kelso, associate professor of politics at the University of Southampton, said: "For a party like the Conservatives, in key marginals that they need to take, such as Southampton Itchen and othersâ€¦ there's quite a lot of work to do to convince those voters to vote Conservative."
Personal circumstances, rather than party loyalty, appear to be a key consideration for some Asian voters.
Ram Kalyan, a community radio station manager from Southampton, said: "I'm an undecided voter. Traditionally our family has voted Labour, but I'm not sure whether that will be the caseâ€¦ I'm now waiting to see what the party leaders are going to put on the table, and then I'll make my decision."
Solicitor Rashidul Islam said it would come down to hard cash: "I have seen more money in my pocket as a result of economic policies this government has, and also my own circumstances - and that's going to dictate it."
In 2013, a study by Operation Black Vote concluded the ethnic vote could determine the outcome of the 2015 general election.
The study found that in 168 marginal seats, the black and minority ethnic vote was bigger than the sitting MP's majority.
Southampton Itchen is a case in point. Labour's John Denham won the seat in 2010 with a majority of just 192.
All political parties say they would like to field more Asian and minority ethnic candidates in order to better represent Britain.
Speaking last year, Mr Cameron said he hoped to see an Asian prime minister in his lifetime.
However, 85% of Asians surveyed told BBC Asian Network they would not vote for a candidate simply because of their race.
Voters said an MP's abilities was a major issue.
"I wouldn't vote for someone just because they're Asian," Rashidul Islam said.
"I would look at what their policies are, what their track record isâ€¦ their own credentials rather than what their background is. If they're Asian, it won't make a difference to me."
The poll also asked about immigration. Some 50% of Asians said they wanted the next government to be tougher on immigration.
Although many respondents were second, third or fourth generation British Asians, EU migration was of concern.
Southampton student Mickey, 26, said: "Britain needs to be more proactive: controlling more strictly how many immigrants come in, what they have to offer, are they good enough for the economy or not - and if not, that's questionable."


A new type of snake has been identified in the UK, bringing the total number of species to four.

Scientists say the barred grass snake, Natrix helvetica, is actually a different species to the common or eastern grass snake, Natrix natrix.
Before, it was thought the grass snake was one species with several subspecies that looked slightly different.
The others native to the UK are the smooth snake and the adder, which is venomous.
Grass snakes are a protected species under the Wildlife and Countryside Act so it is a criminal offence to injure or kill them.
Both types of grass snake are normally found in lowland regions in the south of England. The snakes can be more than a metre (3ft) long, are found near water and eat mainly amphibians like frogs and newts.
The newly distinguished barred grass snake is grey, not olive green like the N. natrix and does not have the same bright yellow collar.
The snake is also found in Switzerland, Italy and France and also has been seen in western Germany.
Along its entire length the N. helvetica has black stripes, which on the common grass snake are barely noticeable.
The Senckenberg Research Institute in Germany led the study into the genetics of more than 1,600 grass snakes.
Professor Uwe Fritz said: "We discovered that the barred grass snake, previously considered a subspecies, is in fact a distinct species.
"We now have to pay close attention to which species of grass snake is involved in each case, in order to be able to assess whether one of them may be more threatened than previously thought."