Keira Knightley admits that she doesn't know who is the more guilty party in her new movie Last Night.
The film sees the actress team up with Sam Worthington and Eva Mendes - Knightley's character doesn't commit infidelity but spends the night with the man she loves while her husbands sleeps with a co-worker.
And Knightley reveals that there were many discussions during the filming of the movie over who is the more guilty party - and she is unable to make up her mind.
Speaking to Digital Spy the actress said: "What is worse? Joanna spends the night in the arms of a man who loves her, and who she loves. He f**ks somebody else. What is worse?" she said.
"We had constant arguments about who was guilty and what was the worst action. Somebody said a great line - 'He tests the marriage, and she breaks it'. I don't know if I agree with that or not, but I can certainly understand it at the same time."
"I vacillate between the two sides. I've got no idea. I rather enjoy not having an idea. I went in absolutely thinking that hers was worse," she explained.
"Somewhere in the middle I thought, 'Well, bloody hell, she doesn't f**k him. What's the problem? They have a nice night, they have a bit of a kiss, she doesn't really do anything'.
"And then I went back to thinking hers was worse. I think it depends on where you are in your life, and that will always change. It's a moveable feast."
Last Night is a second movie for Knightley in 2011 after receiving great reviews for the adaptation of Never Let Me Go.
Last Night is released 3rd June.
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