Keira Knightley’s Atonement costar, James McAvoy, says he’s sheepish at best when it comes to getting intimate in front of the cameras.

“It’s always a nightmare, isn’t it?” he said in a recent television interview. “It’s never easy and it’s always a little bit sweaty and uncomfortable.”

McAvoy, 28, appeared on Britain’s Michael Parkinson show to discuss his role in Atonement. In the film, Knightley, 22, plays Cecilia Tallis, an upper-class beauty who has an affair with the housekeeper’s son played by McAvoy.

The Scottish actor – whom Knightley called the best kisser ever – said he prefers directors to give specific instructions when filming sex scenes. And if they don’t, the situation can suddenly become a bit awkward.

“When they call action, if you feel the lady’s breast, it’s your decision to feel the lady’s breast. It’s like, this is wrong. You have no parameters,” he said.

“What was great about Atonement was Joe Wright [the director] was very, very, very on the ball with what he wanted, so when you were doing something it was at his behest.”

Still, McAvoy and Knightley felt the need to apologize for invading each other’s personal space after the steamy scenes. “We carried on and about 10 seconds later we just said very sheepishly, ‘Sorry about that.’”

Just a FYI, I had a advanced screening of this movie (Atonement) and it is WONDERFUL! The book is awesome and the movie was just beautiful. It goes right by the book pretty much! I say go see it December 9th!