Keira Knightley Spanking scene in Dangerous Method

Talking about the spanking scene on a episode of The Graham Norton Show, Knightley candidly admitted: "Basically it was about spanking. Michael had to spank me."

To which Fassbender, 47, joked: "I was the spanker. You were the spankee."

He explained: "To get the right level of spank, it can't hurt too much, I suppose.

"There was a Yellow Pages between your bum and the paddle!

The Pirates of the Caribbean star, 29, laughed: "I bought Michael and three other cast members their very own spanking paddles.

"I had to go into a sex shop and say, 'Hello, can I have three spanking paddles, please?'"

Well, in an interview with Hollywood Reporter in 2011, Knightley said that she downed a load of shots before filming that scene.

"I read those two scenes and just went, ‘I don’t think that I can do that,’ particularly because it’s the age of the internet," she said.

"It’s gonna be everywhere; I don’t want that out there...I phoned him [Cronenberg] up to turn it down.

"I said to him, ‘Look, I love you, I love the script, I love the character, but I really don’t know that I can play those scenes."

However, the director explained to Knightley that the scenes were going to be 'clinical' rather than 'sexy' or 'voyeuristic in that way'.

"And I thought, ‘Okay, well I can understand that'," Knightley continued. "As long as it’s clinical and it’s not some sort of weird, sexy spanking thing."

She explained: "There was a box which he hit, so he was nowhere near me, thank God!

"I did actually say to Michael before one of the scenes...I was like, ‘I’ve got a security guard outside - you touch me and he’s gonna break your legs!’ And he was like, ‘Keira, you’re tied to a bed. You’re not really in a position to say that'.

"I said, ‘I guess you’re right.’… [I did] a couple of shots of vodka - definitely - beforehand, and then a couple of glasses of champagne as a celebration of never having to do that again!"