In the book released worldwide on January 10, the royal briefly described his first time as an “inglorious episode” and a “quick ride”, but made no mention of whom he had shared it with.

Now Ms Walpole told her side of the story, filling in the gaps left by the Duke and even claiming Harry was actually 16 when he lost his virginity rather than 17 as he penned in the autobiography.

The now mum of two said she had previously met Harry when she worked as a stable girl at Highgrove, King Charles’s countryside retreat.

The pair, who had enjoyed trips together to polo matches, were at a party at the Vine Tree Inn in Norton, Wiltshire, marking Ms Walpole’s 19th birthday in 2001.

Recalling how she felt after seeing her ex-boyfriend walking in the pub with a new girlfriend, Ms Walpole told The Sun on Sunday: “Harry was a friend and knew I was gutted and upset. So when the girlfriend rocked up, he knew how I was feeling.

“He didn’t give me a hug — instead he brought me shots. He brought me some shots to kind of say, ‘Come on, let’s lift the mood’.

“I didn’t see him go to the bar but he came up to me and said, ‘Happy birthday — let’s do some drinks’ not long after this girl got there.

In a different interview with the Mail on Sunday, Ms Walpole claimed it was Harry who made the first move after they left the pub and crept into an adjacent field to have a cigarette.

She claimed: “It was passionate, intense. We both knew. It went from a kiss on to the floor pretty quickly.”

Ms Walpole, who was no longer working at Highgrove when Harry’s first time happened, said she and the Duke did not remain in touch after that night.

Nevertheless, she “didn’t mind” they did not ring each other, as they were not going out together, Ms Walpole added.

While Harry thought the man – whose name is Mark Dyer, his royal aide and mentor at the time – was referring to his first time, Marko actually wanted to know about his drug use, the royal wrote, after a newspaper had told the then-Prince of Wales’s office it had evidence the Duke had used some.

Spare read: “I suspected he was referring to my recent loss of virginity. Inglorious episode, with an older woman. She liked horses, quite a lot, and treated me not unlike a young stallion.

“Quick ride, after which she’d smacked my rump and sent me off to graze.

“Among the many things about it that were wrong: It happened in a grassy field behind a busy pub. Obviously, someone had seen us.”