Katherine Jenkins tweeted this morning about her filming with regular cast members Matt Smith, Karen Gillan and Arthur Darvill (whose name will be in the opening credits from now on). And she will be playing a character, rather than herself.
But I bet more people will be delighted with the casting of Michael Gambon as well for this special, especially given that he was rumoured a few weeks ago to be appearing and now he is. Filming pics should start surfacing within the next few hours, so expect this blog to update you on it.
Press Release: http://www.bbc.co.uk/pressoffice/pressreleases/stories/2010/07_july/12/doctor_who.shtml
Guardian Article: http://www.guardian.co.uk/media/2010/jul/12/doctor-who-christmas-special