Who will be next to take on the keys to the Tardis?
The name of the actor who will replace David Tennant in Doctor Who will be announced on Saturday.
Tennant said in October that he would stand down from the show after filming four special episodes in 2009.
His replacement - the 11th Doctor of the TV series - will be revealed in a Doctor Who Confidential programme on BBC One at 1735 on 3 January.
The casting was confirmed over Christmas and filming for the 2010 series begins in the summer.
Tennant is due to begin shooting the first of his four specials this month, just weeks after surgery on his back.
David Tennant says he is envious of his replacement, whose 'life will change'
The last of these episodes is expected to run in early 2010.
The casting decision has been a priority for the show's new creative team, led by executive producers Steven Moffat and Piers Wenger.
The BBC said that in Saturday's Doctor Who special "the actor playing the new Doctor will be giving his or her initial reaction" to becoming TV's most famous time traveller.
Wenger, head of drama at BBC Wales, said: "We believe the actor is going to bring something very special to the role and will make it absolutely their own.
"I just can't wait to tell everyone who it is - it has been a nail-biting Christmas trying to keep this under wraps!"
THE 10 DOCTORS
1. William Hartnell
2. Patrick Troughton
3. Jon Pertwee
4. Tom Baker (pictured)
5. Peter Davison
6. Colin Baker
7. Sylvester McCoy
8. Paul McGann
9. Christopher Eccleston
10. David Tennant
Shortly after Tennant's announcement, bookmakers were tipping several well-known names as the next actor (or actress) to step into the Tardis.
Murphy's Law and Cold Feet star James Nesbitt emerged as one of the favourites, along with Paterson Joseph, John Simm and David Morrissey - who appeared in the 2008 Christmas special.
Paterson Joseph, who recently starred in Survivors and appeared in two Doctor Who episodes in 2005, has said "any actor would love the challenge" of playing the Time Lord.
Bookmakers made him an early favourite - offering odds of 3-1 on him becoming the first black Doctor.
Comedian Jennifer Saunders, former Doctor Who assistant Billie Piper and film star Catherine Zeta Jones have also been mentioned in connection with the role.
The show's outgoing executive producer Russell T Davies said last month: "Whoever becomes the Doctor has got to take on a whole life. It's not just becoming a part of a TV show."
HAVE YOUR SAY
It would be nice to see an older wiser Dr arrive on the scene. Less cheeky chap and more brilliant eccentric professor.
In October, when Tennant was asked who he thought should replace him, he joked: "Well, I've always been a big supporter of Wee Jimmy Krankie!"
Doctor Who began in 1963, and seven actors played the Doctor before the show was dropped in 1989.
After a TV movie in 1996 - starring Paul McGann - the TV series returned in 2005 with Christopher Eccleston in the lead role. Tennant took over the role the same year.