"And he was like, 'Keira, you're tied to a bed. You're not really in a position to say that.'"
For the actual scenes, Michael ended up spanking a box placed next to her. Keira was initially so wary of her spanking scenes she wasn't sure she could take the role.
She told The Hollywood Reporter: "When I first read the script, I thought, 'The script is fascinating, and it's David, and I really want to work with David, but 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; it's gonna be everywhere; I don't want that out there.' "
She was, however, reassured when he told her the scenes wouldn't be "voyeuristic" or too sexy.
She added: "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.' "
- BANG! Showbiz