December 25, 2008, the air date of The Next Doctor the first of David's Christmas specials without a companion. The title was a nod to the fact that David;s time as the 10th Doctor was coming to an end, there were only the four specials yet to come in 2009.
The episode starred David's other Blackpool co-star as Jackson Lake, the other 'Doctor'. The episode received an 86% audience share with 13.1 million viewers.
Unlike the other Christmas specials which had filmed in the summer, The Next Doctor filmed from April 7th - May 3rd, 2008. The inside of Rev. Fairchild's house was filmed at Fonman Castle, Rhoose and the two Doctor's meet for the first time at The Maltings in Cardiff.
Filming also took place at Tredegar House, which served as home base for Jackson's Doctor. The same location served as Naismith's house in The End of Time and as the school in Human Nature/Family of Blood and numerous other episodes.
The opening sequence when the Doctor first lands in Victorian times was shot in Millers green in Gloucester.
All ten incarnations of the Doctor appear in the info stamp scene. This was the last episode filmed before David announced he was leaving and the first to air after that fact was known.
This is the first Christmas Special that features natural snow. In The Christmas Invasion the 'snow' is actually ash from the the exploding Sycorax ship. In The Runaway Bride the Doctor makes it snow with a burst of energy from the TARDIS and at the end of The Voyage of the Damned the Doctor and Mr. Cooper have the following exchange:
Mr. Copper: You know, between you and me, I don't even
think this snow is real. I think it's the ballast from the Titanic's
salvage entering the atmosphere.
The Doctor: Yeah. One of days it might snow for real.
The Doctor's line is a call back to the fact that the two previous Christmas.