It was a real-life fairytale – the moment, 70 years ago, when two carefully guarded princesses were let loose to join the jubilant crowds in London celebrating the end of the Second World War in Europe. Now the adventure has been re-created in a new film, showing the young Princesses Elizabeth and Margaret as they wander incognito through the city streets. And among the most curious viewers of A Royal Night Out, released next month to coincide with the anniversary of VE Day on May 8, 1945, will be a woman who knows better than anyone what really happened on that extraordinary night. Scroll down for video . Royal Role: Canadian Sarah Gadon, left. plays a young Princess Elizabeth, pictured right . Dancing Queen: Sarah Gadon as Princess Elizabeth enjoying a night out to celebrate the end of the Second World War . Because she was there. ‘It was a Cinderella moment in reverse,’ says The Hon Margaret Rhodes, 89, first cousin to the Queen and her best friend. ‘It was wonderful bedlam. I can’t remember whose idea it was. It was just one of those things that happened.’ Speaking to The Mail on Sunday from her home at Windsor Great Park, she says: ‘I think it’s one of the things that the Queen remembers with great happiness. Neither of them had ever done anything remotely similar, being let loose in a crowd like that to walk all the way from Buckingham Palace through to Trafalgar Square. ‘Everyone was kissing everybody and picking up hats and throwing them away. It was euphoria at its most euphoric!’ Mrs Rhodes, then young Margaret Elphinstone, was lodging at Buckingham Palace while working as a secretary for the military intelligence service MI6. She recalls how a small gang including 19-year-old Princess Elizabeth, Princess Margaret, 15, and Mrs Rhodes’s brothers, left the Palace by the Privy Gate. ‘With the best will in the world, I can’t remember if Princess Elizabeth kissed anyone, but kisses were being thrown about very liberally,’ she says. ‘It was like we had all been living under a huge, heavy, dark cloud. And suddenly, it had gone. I’m so old now, I’m literally the only other person left alive who was there with them on VE Day.’ The Queen is said to remember the night with 'great happiness' In the film, which stars Canadian actress Sarah Gadon as the future Queen and British newcomer Bel Powley as Princess Margaret, the sisters are shown wearing cocktail dresses for their adventure. In real life, Princess Elizabeth was wearing her Auxiliary Territorial Service uniform. Mrs Rhodes says: ‘In order not to be recognised, the Queen pulled her cap right down over her eyes and one of the officers who was with us said, “Look, I’m not going about with an officer who can’t wear her cap properly,” so she had to put it back. Mrs Rhodes adds: ‘I always thought it was very clever of the King and Queen Elizabeth [the Queen Mother] to let the girls go out into the night, with all those myriad of people around them. They knew it was something the Queen and Princess Margaret would never forget.’ Princess Elizabeth is also shown forming a brief attachment with a young serviceman called Jack, who takes her gambling and to a Soho brothel. ‘That didn’t happen,’ laughs Mrs Rhodes, whose younger self does not feature in the film. ‘Apparently, Princess Margaret escapes on the top deck of a bus. That never happened.’ Princess Margaret is also shown quite drunk. ‘No! There was no possibility. We never encountered anyone offering one a drink,’ insists Mrs Rhodes, the daughter of the 16th Lord Elphinstone. One of the true scenes in the film is of the Royal party dancing the conga through the Ritz. ‘The smart old ladies having drinks were gobsmacked,’ says Mrs Rhodes, although it actually happened on VJ night, August 15 – when Britain celebrated Japan’s surrender. The princesses were protected on their VE Day jaunt by Captain Harold Campbell RN, equerry to Princess Elizabeth’s father, King George VI. ‘He was deeply disapproving of the whole manoeuvre,’ says Mrs Rhodes. The party returned to the Palace after midnight. ‘It was emancipation,’ says Mrs Rhodes. ‘I don’t think anybody realises what she has had to give up. You give up your independence. Poor Princess Margaret is dead, but that night is something I know the Queen will never forget.’ ...And she recorded a secret song tape . Friends: Margaret Rhodes, left with Princess Margaret and Elizabeth, right . By Michael Powell . The Queen and Princess Margaret recorded a secret tape of children’s songs as a touching gift for their mother on her 90th birthday, it has been revealed. Pianist and composer Laurie Holloway has told for the first time how his friend Princess Margaret phoned him with the idea, days before the Queen Mother’s milestone birthday in August 1990. He was summoned to Buckingham Palace and taken to an upstairs room ‘where there was a dark brown, walnut grand piano and two microphones. There was also a sound engineer who I think they had got in from the BBC’. Mr Holloway said the Queen, then 64, and Princess Margaret, then 59, wanted to sing quite unusual children’s songs. ‘One was called I Know Where The Flies Go In Winter Time,’ he said. ‘The Queen said they were taught them by their mother’s father, the Earl of Strathmore. We rehearsed them a few times and then we recorded them in one take each.’ Mr Holloway, 77, musical director on Strictly Come Dancing for its first three series, said the Royal sisters sang ‘very well, beautifully in fact’ during the two-hour recording session. ‘The Queen has a nice, sweet tone to her voice,’ he added. He said Margaret told him the Queen Mother loved the gift. ‘She said that when they gave it to her at Windsor, the Queen Mother said she didn’t have anything to play it on, so they had to go out to the car to listen to it. ‘Later, Prince Charles arrived and wanted to listen to it. They told him he would have to go out to the car and to everyone else’s surprise he opened a cupboard and there was all the latest stereo equipment right there.’ Sadly, the cassette went missing after the Queen Mother’s death in 2002, although Mr Holloway wonders if a copy might still exist somewhere.
Princess Elizabeth and Margaret joined the crowds celebrating in London . Queen's cousin Margaret Rhodes was with the young royals celebrating . She says the Queen remembers the night with 'great happiness' Adventure has been recreated in new film A Right Royal Night out .