Keira Knightley is happy to bear her breasts on camera - because they are ''so small''.

The 27-year-old actress - who is engaged to Klaxons star James Righton - has a strict ''no bottom'' clause in her contracts, but doesn't mind stripping above the waist because she thinks people aren't very interested in her figure.

She said: ''No bottom half! I don't mind exposing my breasts because they're so small - people really aren't that interested!

'''But] I think it's much easier as you get older. You can say, 'No.' 'Yes.' 'No.' ''

The 'Anna Karenina' actress admits she is usually amused to see movie bosses ''pencil in'' curves for film posters - but she was furious when she was left with ''droopy t*ts'' on the promotional materials for 2004 production 'King Arthur'.

She told the December issue of Allure magazine: ''They always pencil in my boobs.

''I was only angry when they were really, really droopy.

''For 'King Arthur,' for a poster, they gave me these really strange droopy t*ts.

''A... I don't have t*ts anyway and B... they digitally made them, and I thought, 'Whoa!'

''It's my face on that poster. I thought, 'Well, if you're going to make me fantasy breasts, at least make me perky breasts.' ''