David Tennant has confirmed he will be stepping down as the Doctor. The four 60-minute specials being made in 2009 will mark his last appearance as the character, indicating he will regenerate at the end of the 2009 Christmas special, with the new Doctor taking over for Season 5 in early 2010.
Tennant is the tenth actor to play the role, following on from William Hartnell (1963-66), Patrick Troughton (1966-69), Jon Pertwee (1970-74), Tom Baker (1974-81), Peter Davison (1981-84), Colin Baker (1984-86), Sylvester McCoy (1987-89), Paul McGann (1996) and Christopher Eccleston (2005). The Doctor, a Time Lord from the planet Gallifrey, is capable of 'regenerating' when his body sustains wounds which would kill an ordinary human. However, he can only regenerate twelve times before dying. The current Doctor Who production team have suggested that they won't let this limitation prevent them from telling stories in the future.
The series originally ran for 26 seasons from 1963 to 1989 before returning for a one-off special in 1996 and then a new series beginning in 2005. The 2007 Christmas special won audiences of over 13 million, making it the most successful British drama series of modern times.