Knightley Scared To Bare Bottom

British beauty Keira Knightley is insecure about her body - and refuses to bear her naked bottom in front of the camera.

The KING ARTHUR screen siren recently filmed her first sex scenes in movie The Jacket, and she was anxious to have as few crew members on set as possible.

The 19-year-old recalls telling a director, "You're not going to see my a*se! The top half is fine but the bottom half isn't. It's a girl thing. You know, it's just one of those things."

Knightley jumped at the chance to star alongside OSCAR-winner Adrien Brody in The Jacket because it was unlike any role she'd been offered before.

She says, "When I read this script the character was different from anything I had played before and was just really, really exciting."

Before her first sex scene, Knightley made special arrangements with director John Maybury: "It was kind of the first time I had done a nude thing. It was cool. It was only John, the cameraman and the focus-puller, so there were only three people."