London, Mar 27 : Hollywood actress Keira Knightly has revealed that she couldn't stop laughing while filming sex scenes for The Duchess.

The 24-year-old actress said she had fits of giggles when her co-star Dominic Cooper, 30, had to act in a nappy.

"During the sex scene I was luckily fully clothed, but he had to wear this skin-coloured nappy," the Sun quoted Knightley as saying.

"Sex scenes are never the easiest and you're meant to be very supportive of each other, but I just completely lost it.

"The director had to tell me, `Pull yourself together'," she added. (ANI)