Keira Knightley becomes a reindeer on Christmas Day

British actress Keira Knightley is to turn into a reindeer this Christmas, and it's all in the name of charity. She has lent her voice to Em, a reindeer in the popular UK Christmas animation Robbie The Reindeer, who returns to the BBC for his third festive adventure this year. Other famous voices to be heard during the episode, entitled Close Encounters of the Herd Kind, include Ardal O'Hanlon, Jane Horrocks and Michael Palin. Written by Love Actually, Blackadder and Four Weddings and A Funeral writer Richard Curtis, all proceeds from the sales of the DVD go to UK charity Comic Relief.

Here's Keira's character Em: