James McAvoy has had the 'hint of an erection' when filming sex scenes.
The 33-year-old actor has filmed intimate with some of the world's most desirable ladies including Angelina Jolie and Rosario Dawson but says the hardest were with his fututre wife, Anne-Marie Duff, for British TV series 'Shameless'.
He told The Guardian newspaper: 'We weren't together yet. I fancied her, but you don't want to make that person feel like they're being abused or that you're enjoying yourself.
'I've had the merest hint of an erection a couple of times, but its usually so uncomfortable that it's more about making it look like you're really going for this person, while convincing the person that you're not having a good time. While at the same time not making them feel like you're saying 'Don't worry, I'm not enjoying it, because you're f***ing stinking!'
The 'Welcome to the Punch' star says the way actors treat sex scenes varies, and he knows of one high profile American actor who rubs his hands before sex scenes and says 'Way-hey, free cheatin'.'
James and Anne-Marie married in 2006 and have two-year-old son Brendan together, who they take it in turns to look after while the other is working.
James said: 'My wife and I want to work, but we also want to make sure that one of us is at home with the family. So we take it in turns a little bit.'
