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But Kinnear, whose odds were at 5-1, has previously denied rumours he will be next to step into the Tardis, insisting last month that "it's all bull****".

Sources close to the show said only 10 people knew the name of the new Doctor, which will be unveiled in a one-off live show at 7pm tomorrow, to be hosted by Zoe Ball.

The chosen actor will be interviewed in front of a live studio audience and a few Daleks, with previous Doctor Who stars also present.

Even the plans for tomorrow's half-hour show were originally kept secret, with a repeat of Celebrity Mastermind put in listings in its place.

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

A William Hill spokesman said yesterday: "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."

Ben Stephenson, controller of BBC drama commissioning, said: "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 at the moment have no idea they are in the presence of the 12 incarnation."