Keira Knightley - Knightley Joined Never Let Me Go To Work With Mulligan

The British actresses met when they played sisters in the 2005 re-telling of Jane Austen's classic love story Pride & Prejudice and have remained close ever since.

They teamed up again in 2009 to shoot a big screen adaptation of Kazuo Ishiguro's haunting novel, which tells the story of friends at an English boarding school who share a tragic secret, and the film has been tipped for awards season success.

And Knightley admits she took the role in the drama after learning she'd be onscreen with Mulligan once again.

She tells Britain's Telegraph magazine, "Carey was one of the reasons I wanted to do this. She and I worked together on Pride & Prejudice and we've been friends ever since. We've been on holiday together.

"It's rare you get the opportunity to work with people who are friends. When you play characters like this, that have the relationships they do, it's lovely working with someone with whom you have a shorthand and a history."