Keira Knightley's foul mouth

Keira Knightley "enjoys" swearing.The 23-year-old star - who claims she doesn't drink, take drugs or smoke - revealed she picked up her only bad habit from her mother, playwright Sharman McDonald. Keira, who has appeared in period dramas including 'The Duchess' and 'Pride and Prejudice', told Britain's Daily Mirror newspaper: "That is my vice, swearing, and I really enjoy it. And you know what, my mum swears quite a lot, while my dad does not swear."She also talked about rumours she may appear as Eliza Doolittle in a remake of 'My Fair Lady' opposite George Clooney, saying: "It's an interesting prospect, but there's nothing concrete yet."The actress has also revealed she is not ready to marry her actor boyfriend Rupert Friend, 26, adding: "Marriage is a big thing for a lot of women, but not me. I don't have plans. You never know what's going to happen day to day so you might as well just deal with it as it happens."Keira's next role will be as author F. Scott Fitzgerald's wife Zelda in an adaptation of his novel based on their lives, 'The Beautiful and the Damned', which will start filming next year.