James McAvoy has revealed his sex scenes with Keira Knightley were a "sweaty and uncomfortable nightmare".
The 28-year-old actor felt so awkward while filming the raunchy scenes for 'Atonement' he kept apologising to Keira when the cameras stopped rolling.
James said: "It's always a nightmare filming sex scenes, isn't it? It's never easy and it's always a little bit sweaty and uncomfortable.
"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.
"We carried on and about 10 seconds later we just said very sheepishly, 'Sorry about that'."
The 'Last King of Scotland' star - who Keira described as "the best kisser ever" - was pleased director Joe Wright ordered them around during the passionate scene.
He said: "What was great about 'Atonement' was Joe Wright was very on the ball with what he wanted, so when you were doing something it was at his behest."
James has just finished shooting 'Wanted', in which he plays a young man who learns that his long lost father is an assassin.