had to down vodka for Dutch Courage before filming her raunchy spanking scene in 'A Dangerous Method'.
The 26-year-old actress was so worried about the scenes with Michael Fassbender
she had to have a drink to calm her down beforehand.
She said: "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."
In the film Keira plays Sabina Spielrein, a Russian who has a love affair with psychoanalyst Carl Jung - played by Michael - and she admitted her nerves even made her threaten he co-star.
She added: "I did actually say to Michael before one of the scenes, '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.'"
Keira never actually got spanked in the scenes, with Michael instead hitting a box which was box placed next to her.
Keira nearly turned down the role because of the sexy scenes, but was talked around and reassured by director David Cronenberg.
She added to The Hollywood Reporter: "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.'
"He said, 'Look, if I'm gonna do them, then they're gonna be clinical; they're not gonna be sexy, they're not gonna be voyeuristic in that way.'
"And I thought, 'OK, well I can understand that. As long as it's clinical and it's not some, sort of, weird sexy spanking thing.' "