Keira Knightley's nappy sex

Keira Knightley's nappy sex

Keira Knightley's co-star wore a flesh-coloured nappy for their sex scene in their new movie.

The 23-year-old actress collapsed in a fit of giggles when Dominic Cooper, 30, stepped out in the unflattering underwear for 'The Duchess'.

Keira said: "We are all meant to be supportive of each other in these difficult and embarrassing scenes, but I took one look at him and just lost it.

"I couldn't stop laughing because Dominic was trying to be dignified and aloof while looking completely ridiculous. The director came over and said, 'Pull yourself together. This is serious work.' "

Despite being embarrassed by Keira's reaction, Dominic admits his costume was not the most attractive of items.

He said: "On screen, it looks as if I am naked, but in reality I was wearing a flesh-coloured nappy which is held in place by being taped to my inner sanctum.

"And what did Keira do when she saw me? She burst out laughing. Unbelievable!"