So Matt Smith is the 11th Doctor Who. Not John Simm, David Morrissey, James Nesbitt, Russell Tovey, Paterson Joseph, James McAvoy or, thank the Lord, David Walliams. Not Amy Winehouse, Catherine Zeta Jones or Lesley Sharp, all of whom were - somewhat mischeviously - suggested by outgoing showrunner Russell T Davies. After months of agitated speculation, we now know that the universe's favourite - and until the plot demands it, its only - Timelord will next be played by an actor best known for a role as a New Labour researcher.

Matt Smith, 26, is the youngest actor ever to take the role of Doctor. Known primarily for playing Danny Foster in Party Animals he's also attracted attention for a striking turn as a son in an incestuous relationship with his mother in Polly Stenham's play That Face.

With his identity revealed on BBC 1 this evening, Smith said he was 'flabbergasted' to get the role. "I haven't slept", he said. "It's an iconic part of our culture… it has the status of Robin Hood or Sherlock Holmes and I'm taking it on. It's nerve-wracking and exciting, I'm flabbergasted. It's a huge legacy [but] I want to be brave enough to make my own choices."

Smith, who shares Tennant's appealing gangliness, was born in Northampton in 1982 and studied drama and creative writing at the University of East Anglia. He he later avoided drama school, but became a member of the National Youth Theatre. His role in That Face, opposite Lindsay Duncan, at the Royal Court in April 2007 earned him a nomination as best newcomer at the Evening Standard Theatre Awards. He already has a connection with Doctor Who, having starred alongside Billie Piper in BBC1's adaptations of Philip Pullman's Sally Lockhart novels The Ruby in the Smoke and The Shadow in the North. (He also appeared with Piper in an episode of Secret Diary of A Call Girl).

With the role finally cast, the BBC decided that the secret could only be kept for so long . That the announcement occurred on the same evening as ITV1 launches its own new teatime drama Demons is entirely coincidental. No attempt at stealing thunder or at schedule sabotage, there.

The news has been a long time coming. Making Doctor Who is exhausting and the creative team in front of and behind the scenes have long made clear their desire to move on to new projects. Arguably, that weariness has lately been visible on the screen, so change is good. Still, you can understand actors' reticence about taking on the role. Tennant has been such a definitive doctor that there will be those who have forgotten all about Christopher Eccleston. Further, the commitment required - the gruelling filming schedule and the ardent Who fans that one must court or at the very least tolerate - coupled with the intense tabloid scrutiny that playing the Doctor inevitably attracts aren't exactly incentives for taking on the role. Actors who feel their careers have potential in Hollywood may have eschewed Wales for obvious reasons.

Then again, playing the Doctor has catapulted Tennant into British TV drama's A-list. Similar things can be said of a post-Rose Billie Piper and even a guest appearance in Doctor Who can work wonders for an actor's career. Expect to see a lot more of Dervla Kirwan after her appearance in The Next Doctor at Christmas. Plus, you get a doll of yourself and how exciting is that?

Then there's the opportunity of working with Steven Moffat, one of the most exciting writers working in the UK – and if his transitory attachment to Steven Spielberg's Tintin trilogy is indicative of anything, one of the most exciting writers in the world. Moffat's Doctor Who episodes – The Empty Child, The Doctor Dances, The Girl in the Fireplace, Blink, Silence in the Library and Forest of the Dead – have been among the strongest and darkest of the series under Russell T Davies. They've also been among the smartest, confirming that Moffat has both a dark and a light touch. His stories tap into childhood fears – of the dark, of what happens when you close your eyes, of the sinister weight an innocuous phrase can accumulate when repeated, as in The Empty Child's "Are you my mummy?". His tales contain wonderfully witty and tender moments, addressing big issues but tending to delightful detail. The speech given by Professor River Song in Forest of the Dead that begins "Everybody knows that everybody dies…" was one of the most touching on television last year.

Of course, there's a year, and four specials, to go before the Doctor regenerates from Tennant into Smith. Tennant's back injury permitting, the first of those schedules is scheduled for Easter and they're already providing grist to the gossip mill. There's rumour that at least one will be filmed in America while another is said to be destined, bizarrely, for Dubai. (I'm sceptical of this given Russell T Davies's commitment to gay rights and homosexuality being a crime in the United Arab Emirates.) Also a topic for discussion will be how long Smith has signed up to play the Doctor for. Smith, 26, could be Christopher Eccleston all over again. But now that we know who the new Doctor will be – for one series at least - the next maelstrom of giddy speculation can begin in earnest: the identity of his new companion. The smart money's on Gina Bellman. Or Michelle Ryan. Or…