Filming has begun on this year's Christmas Special, which Steven Moffat has described as the "most Christmassy ever". Set in midwinter during WWII, the Doctor is the caretaker of a "creepy old house in Dorset", and will embark on adventures with Madge Arwell and her two kids Lily and Cyril, which include a chase through a 'Lion, the Witch, and the Wardrobe' type forest, complete with an icy villain.

http://www.doctorwhonews.net/2011/09/dwn200911224008-christmas-guest-stars.html