It was a day for resignations yesterday(*), starting when Russell Brand finally decided he didn't want to prolong the agony at Radio 2. Under all that kerfuffle the real news (for Whovians at least) was almost buried, coming as it did late by video link to the National Television awards (where ironically Tennant won the award for outstanding drama performance award and Doctor Who once again won most popular drama), and breaking on the late night TV news bulletins.

So much of the world will be waking to the news for the first time this morning: the Doctor is dead, long live the Doctor. Tennant has moved on and now we will not be able to avoid the endless and tedious speculation about who will be the 11th Doctor, until one of the prime suspects - or a complete outsider - is nominated.

Tennant will, of course, star in the Doctor Who Christmas special this year (it's already been filmed, so it would be hard for him not to!) and the BBC has confirmed that he will be sticking around as the Doctor in the four specials that pass for a "2009 series" but that will then be that, as the most popular Time Lord ever (according to some polls) regenerates in time for the next full series in 2010 and, incidentally, in time for new head writer Stephen Moffat to take up the reins.

His resignation speech included the comment that: "It would be very easy to cling on to the Tardis console forever and I fear that if I don't take a deep breath and make the decision to move on now, then I simply never will." I agree wholeheartedly; it was time for him to go. Yes, he's acclaimed as the best Doctor ever. Yes, he's hugely popular. Yes, he's helped take the show to new places and assured it of a new, young, modern audience for years to come. But even in the face of all that many fans, myself included, were already beginning to tire of his gaping-mouthed goggle-eyed portrayal of the last of the Gallifreyans and to start to think that he was playing it by the numbers.

There's always an element of frying pan and fire with such changes though, and attention will now inevitably move on to the question of who will replace him. Speculation has been rife ever since Russell T Davies announced he was leaving the programme, with James Nesbitt apparently always a front runner, but with names like Chiwetel Ejiofor and John Simm also in the frame. Once thing is certain, this won't be the last article you read about "who is going to be the next Who?" this year.

(*) Big resignation news like this usually comes in threes (they say), so who will be the third big name to go today? Jonathan Ross? I don't think so, but who else is teetering on the brink?