|Colin Farrell and Kate Beckinsale|
She said: "I've done it with somebody else in front of my husband before so I think it was actually much more awkward for Colin. He was the one who was like, 'Are we done? Are we good?'
"I think it's easier for a woman as we don't have any moveable parts. You can just sort of blank out and nobody can really tell what you're thinking. I think it's much harder for boys maybe - or not."
The 'Underworld' star also revealed she gets more jealous than her husband - who she married in 2004 - and would never let him appear in a sex scene.
In an interview with The Sun newspaper, she said: "It's nice that Len is not very jealous and can be relaxed about me doing these scenes, but he would never be allowed to do that.
"It's quite strange being directed by him, actually, because normally he's taking direction from me at home. He never knows where anything is and he can't remember if he likes parsnips and things like that. Anyway that's our life so it's quite a gear change."