(Cover) - EN Showbiz - Keira Knightley had a no touching' rule while filming a scene where she is spanked for her new film.

The British actress shot several kinky sequences with Michael Fassbender for A Dangerous Method. In the movie, Keira is psychoanalyst Sabina Spielrein, while Michael plays scientist Carl Jung.

One scene involved Carl striking Sabina, and Keira has revealed it was a challenge for her.

"I actually said to him before we shot the spanking scenes, 'If you touch me I will kill you,' and he did remind me that I was tied to a bed at the time and really I shouldn't be making any threats," she said at the premiere for A Dangerous Method at the BFI London Film Festival last night.

"The film is about so much more than S&M but [those scenes] weren't particularly easy."

Keira looked stunning at the premiere in a black and cream Roksanda Ilincic dress and Salvatore Ferragamo high heels.

The 26-year-old beauty was thrilled to work with director David Cronenberg, on the movie about the tense relationship between Carl and Sigmund Freud.

She described the role as a "dream come true" and insists she intends to continue challenging herself.

"It's important to push yourself. I don't want to do the same thing again and again and again and I don't think people really want to watch that, and sometimes I'm going to fall flat on my face and I think I have done that, and will continue to do that but hopefully there will be some gems in there that are really interesting as well," she added. (C) Cover Media