It was during The Deadly Assassin (1976) that we learnt TimeLords are able to 'regenerate' only twelve times before they die. Fandom and viewers alike have therefore always assumed that the Doctor's 13th body would be his last, but a passing comment in The Sarah Jane Adventures later this month will redefine TV history by now making the Doctor immortal!
In the 2-part CBBC spin-off story, The Death of the Doctor, Clyde (one of ex-companion Sarah Jane Smith's proteges) asks the current Doctor how many times he can regenerate. The Doctor casually indicates that there is in fact no limit.
Way back in Tom Baker's tenure, Doctor No. 13 would have seemed light years away, but with the 11th Doctor now here, moving the goal-posts was inevitable.
Only recently, JK Rowling admitted that once a hero has conquered the world, he [Harry Potter] never truly goes away. Even Conan Doyle was forced to resurrect Sherlock Holmes from the dead.
Does the last of the TimeLords now share the same ability to live forever, as Captain Jack Harkness? I suspect that Torchwood creator Russell T Davies has wanted to address this issue since Doctor Who returned in 2005.
Unlike the late 1980's, the present BBC execs are thankfully reluctant to end their ever expanding flagship drama programme.