The Aussie actress writes about the shocking incident in her new memoir, Rebel Rising, claiming that it had unfolded in 2014 at a US tech billionaire’s home, reported the UK’s Telegraph.

“I got thrown a last-minute invite to a tech billionaire’s party – the guy who invited me, who’s like fifteenth or twentieth in line to the British throne, had said to my male friend, ‘We need more girls’,” Wilson claimed, without identifying the royal in question.

It’s unlikely a person that far down the list of succession would be a senior working royal.

She added that the medieval-themed event had taken place at a rented ranch outside Los Angeles, and she’d worn a “buxom damsel outfit complete with cone hat”.

Wilson went on: “The party was insane. Men were jousting on horses in a field, girls dressed as mermaids were in the pool … The property was massive, and because it was quite a drive, people had been assigned rooms to sleep there overnight”.

The Pitch Perfect star added that she watched the British royal “flounder” during the party before things took a turn.

“There’s a huge private fireworks display and then all of a sudden it’s 2am and a guy comes out with a large tray piled with what looks like a tonne of candy,” Wilson explained.

“I’m like, ‘Ooooh, is that candy?’ and the guy holding the tray says, ‘No, this is the molly [MDMA],’ and I turned to the screenwriter I’ve been talking with, confused. He says, ‘Oh, it’s for the orgy … the orgies normally start at these things about this time.’”

Wilson added: “Now the comment by the Windsor about needing more girls started to make a lot more sense. They weren’t talking about a boy-girl ratio like it was a year-eight disco. They were talking about an ORGY!”

Rebel Rising was originally slated for release in Australia on April 3, but has been pushed back until May 8.

It was initially supposed to coincide with a press tour, but the star announced to fans last week that it had now been cancelled due to her “changing work schedule”.