Did Queen Elizabeth II go on a secret night out as a young Princess? After watching the final instalment of The Crown, it’s something we’re more than curious about – and is a query with a very surprising answer.

So, listen to our warning. You might want to put down any cups of tea you’re holding for this one. The Queen did in fact enjoy a night out in London to celebrate the end of World War II in Europe back in May 1945, as The Crown suggests.

Princess Elizabeth, then 19, and her sister Princess Margaret, 14, enjoyed a remarkable night out together, going incognito among the public while the country celebrated the historic occasion. The late Queen said it was “one of the most memorable nights of my life” and it’s no wonder, based on her recollections and the stories shared by friends who joined her.

With the blessing of their parents, the young royals were given special permission to join the crowds partying outside the Palace gates. Then, together with a group of 16 members of the royal household, the royals made their way across London.

Reflecting on the occasion as part of a Channel 4 documentary in 2015, the Queen’s cousin, The Hon Margaret Rhodes, said: “We crossed the forecourt at Buckingham Palace and got to the railings and there were these masses and masses of people. There was a general thing of, ‘We want the King and Queen’, which we all frantically joined in with and were amazed when, five or 10 minutes later, the windows opened and they came out onto the balcony. It was like a wonderful escape for the girls. I don’t think they’d ever been out among millions of people. It was just freedom – to be an ordinary person.”

What followed was an evening of fun, laughter, and surprising firsts (including a disguise gaffe) as the group set off on an adventure. As the late Queen told the BBC, “We were terrified of being recognised – so I pulled my uniform cap well down over my eyes. A Grenadier officer among our party of about 16 people said he refused to be seen in the company of another officer improperly dressed. So I had to put my cap on normally.”

Fortunately, it sounds like the group’s efforts were well rewarded, as they were quickly swept up in the crowds. Queen Elizabeth remembered “lines of unknown people linking arms and walking down Whitehall, all of us just swept along on a tide of happiness and relief. I also remember when someone exchanged hats with a Dutch sailor; the poor man coming along with us in order to get his hat back.” But the evening did not stop there for the group had a glamorous designation in mind: The Ritz.

“For some reason, we decided to go in the front door of the Ritz and do the conga,” Rhodes recalled. “The Ritz has always been so stuffy and formal – we rather electrified the stuffy individuals inside. I don’t think people realised who was among the party – I think they thought it was just a group of drunk young people. I remember old ladies looking faintly shocked. As one congaed through, eyebrows were raised.”

Finally, the party returned to Buckingham Palace, walking though the Royal Parks. Jean Woodroffe, a former lady-in-waiting told Channel 4, “There were places like Green Park and St James’s which one would never have walked through at night in the war – and there we were. There was the usual thing of people kissing and hugging – and even making love. I was shocked by it – I hadn’t experienced that sort of thing happening before in public.”

And, to mark the momentous day, King George VI made a second appearance on the balcony, which his daughters watched from below (where an estimated 50,000 people had gathered by midnight).

“We were successful in seeing my parents on the balcony, having cheated slightly by sending a message into the house, to say we were waiting outside,” the Queen told the BBC.

In sharing her story, the Queen also let the public see a different side to her, says biographer, historian and broadcaster Sarah Gristwood.

“It does show that more playful, comic, adventurous side to Elizabeth that those close to her described,” Gristwood told Cosmopolitan UK, a side she says the public didn’t get to see much, excepting, of course, for a few glimpses, like when she starred in that sweet Paddington sketch during the Platinum Jubilee.

Either way, it sounds like the party had a royally good time, so much so the incredible story is almost difficult to believe.