A Downton Abbey Christmas Special to air on Christmas Day on ITV

Merry Christmas from Downton Abbey!

The 2-hour Christmas Special episode for Downton Abbey with (as Matthew's mother Isobel Crawley) co-starring and appearing in the special 2-hour holiday episode will air Christmas Day (December 25th) on ITV.

UPDATED 12/22/11: According to PBS Masterpiece (via facebook),  Downton Abbey, Season 2 finale (also known in the UK as the Christmas special) will air in the US on Sunday, February 19, 2012 on PBS Masterpiece Classic.
  
From recent released Press Pack (via ITV):

Christmas 1919:
Downton Abbey is hosting a lavish Christmas party, yet despite being the season of goodwill, tensions are rife and Bates’s arrest has cast a shadow over the festivities. Will he be a condemned man or will he be found innocent in time to dance with his new wife at the annual servants’ ball?

Mary has to consider her future with Sir Richard Carlisle following a contretemps at the shooting party and Violet has concerns about Rosamund, whose new suitor - the dashing but raffish Lord Hepworth, is not all he seems.

Downton Abbey Christmas Special stills
featuring Penelope Wilton as Isobel Crawley

    (source: ITV | Period Movies )

View more stills from the Christmas episode here (via Period Movies on FB).