A 40-year-old digger driver has identified herself as the woman who took the Duke of Sussex's virginity in a muddy field, having kept the five-minute, "wham bam" liaison secret for 21 years.
Sasha Walpole, a mother-of-two, said the Duke could have warned her that he was going to reveal the details in his memoir, Spare.
She said she found out he had described the "inglorious episode" via a WhatsApp message from a friend, admitting it was "surreal" to have finally been exposed and that "panic" set in, prompting her to seek legal advice.
"I don't understand why he went into such detail," she said. "He could have said he lost his virginity and left it at that. But he described how it happened - in a field behind a pub.
"That's fine if you're not the other person involved. But if you're me, then you suddenly feel as if your world is getting a little bit smaller."
Ms Walpole said she would never have spoken out if the Duke had not exposed her, as she was "not that sort of person" - adding: "He has brought it to my door by writing about it."
In a joint interview with The Sun and the Mail on Sunday, Ms Walpole said: "It is his story, and he's entitled to write what he wants. He didn't name me but people who were there that night, or simply part of that social circle, would be able to work out it was me.
"Possibly, Harry could have thought about that before publishing. He could have found me if he had tried."
The Duke was 16 at the time and Ms Walpole was 18, turning 19 the following day.
He described her in the book as an "older woman", sparking a global guessing game about her identity.
He wrote: "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."
Ms Walpole said: "I kept this a secret for 21 years. I did it because Harry was a friend, regardless of whether he's a Prince or not. I didn't invite any of this attention, but I know the hunt would have kept going until people found me.
"Panic cut in. I live in a quiet area and it got to the stage when a strange car drove by, I'd think: 'Is this it?' I worried that I'd wake up one morning and find a barrage of cameras outside my house."
She said that because so many friends knew it was her, she felt she had to "take control of the situation before it took control of me".
The incident took place at The Vine Tree pub in Norton, Wilts, on July 21 2001.
The Duke - then an Eton schoolboy - got to know Ms Walpole, an assistant groom at Highgrove, the King's Gloucestershire home, two-and-a-half years earlier through their shared love of horses.
They shared a wider group of teenage friends who attended the same polo matches and hunt balls and often socialised in the local pubs or at Club H, Harry and William's basement den at Highgrove.
On the night in question, Ms Walpole had invited Harry to the pub to celebrate her 19th birthday.
The Duke gave her a stuffed Miss Piggy toy he had won at Thorpe Park earlier that day and a comedy birthday card.
He bought a tray of 10 shots - five each - which they shared before he asked if she wanted to go outside for smoke.
She recalled: "He started to kiss me. It was passionate, intense. We both knew. It went from a kiss on to the floor pretty quickly.
"It was instant, fiery, wham bam, between two friends. It was sparky because we shouldn't have been doing it. He wasn't 'Prince Harry' to me, this was Harry, my friend, and the situation had got a little bit out of control. It felt naughty, I suppose, in the sense that it shouldn't be happening.
"We didn't set out to do it - it wasn't premeditated and I didn't know he was a virgin. There were no virgin vibes - he seemed to know what he was doing. It was quick, wild, exciting. We were both drunk. It wouldn't have happened if we weren't."
Ms Walpole said it lasted "about five minutes". She admitted giving the Prince a smack on the bottom, recognising his description in the book.
"It's his sense of humour," she added. "[We were part of] a massive horse scene and the slap happened in a horsey context, the book is a funny interpretation of that. His description is accurate - the real shock when I saw what he'd written was how true it was. That's what took me back the most. I'm not offended."
The pair separated as they returned to the pub to avoid detection, but Ms Walpole had to return to the field with a friend the following day to retrieve her belt.
Despite their friendship, she revealed that she had not seen nor heard from the Duke since that night.
She has since swapped the world of horses to follow in her father's footsteps and become a digger driver. She revealed she had confided in her parents as well as her husband, Ian, a racing driver, about the liaison with the Duke but that they had kept her secret.
Meanwhile, actor Rupert Everett has claimed that Prince Harry did not lose his virginity that night but in another country, teasing in an interview with The Telegraph that he knew the identity of the woman in question.
"I'm just putting it out there that I know," he said.