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Bookmakers have suspended betting on the new Doctor Who because they are convinced Peter Capaldi has got the job.

The actor, famous for his role as foul-mouthed Malcolm Tucker in The Thick of It, was down to 5/6 favourite with William Hill when they stopped taking bets.

Joe Crilly, a spokesman for the firm, said: “We have seen people today trying to back Peter Capaldi as much as possible at every price available and after a small gamble on Daniel Rigby overnight, it seems that Capaldi is once again in line to move into the Tardis.”

The identity of the latest star to play the time lord will be unveiled live on television on Sunday amid tight security in a bid to prevent the identity leaking out.

Sources close to the show said only 10 people know the name of the new doctor, who will replace Matt Smith, and they are using the codename Houdini to try to keep it a secret.

Capaldi is a life-long fan of the show and even wrote a letter to the Radio Times about the Daleks when he was a teenager.

Plans for Sunday’s half-hour show, which goes out at 7pm, were kept secret with a repeat of Celebrity Mastermind put in listings in its place.

The show will be presented by Zoe Ball and feature interviews with Smith and executive producer Steven Moffat as well as celebrity fans and some previous incarnations of the science-fiction hero.

Other names that were mentioned as possible contenders include Daniel Rigby, whose award-winning performance as Eric Morecambe in Eric and Ernie beat Smith to the best actor TV Bafta in 2011, and Cutting It star Ben Daniels.

Read: Five people who definitely won't be the next Doctor

Mr Moffat said: “The decision is made and the time has come to reveal who’s taking over the Tardis. For the last of the Time Lords, the clock is striking 12.”

BBC drama controller Ben Stephenson said: “We can’t wait to unveil the next Doctor. Amongst all the speculation and betting, there has been lots of fun and intrigue at work as we’ve been using the codename Houdini as a decoy.

“It’s the biggest secret in showbiz, even those working with the new Doctor on other projects have no idea they are in the presence of the 12 incarnation.”