Keira Knightley has said that she found it hard not to laugh during sex scenes in The Duchess.

The actress, 24, claimed that she couldn`t stop giggling because of the outfit that co-star Dominic Cooper was forced to wear during the intimate moments.

"During the sex scene I was luckily fully clothed, but he had to wear this skin-coloured nappy," she told The Sun.

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

She added: "The director had to tell me, `Pull yourself together`."

Source: http://www.whosdatedwho.com/news/story_view.asp?ID=23314