Vaughan will take over the show in March 2004

Vaughan has signed a three-year deal to present a programme that attracts audiences of over 1.5 million a day.

"I'm used to early mornings so getting up won't be a problem," he said. Chris Tarrant praised Vaughan as "vibrant, lively, funny and exciting".

Meanwhile Vaughan will host weekly debate show Fighting Talk on BBC Radio Five Live from Saturday.

The announcement of Vaughan's new role comes after months of speculation that Tarrant - who has been at the station for 17 years - was leaving Capital's flagship show.

"This has been an incredibly important decision for us. Chris Tarrant has been with the company for 17 years and he's certainly an impressive act to follow," Capital Radio chief executive David Mansfield said.

"However, I believe that Johnny is simply the best presenter to take over the biggest show on London's leading radio station," he said.

'Thrilled'

Vaughan, 37, signed a �3m deal with the BBC that ends in May 2004. He hosted a talk show on BBC Three and also starred in a sitcom, 'Orrible, that suffered poor ratings.

Tarrant, meanwhile, will continue to host the ITV1 quiz Who Wants to be a Millionaire?

He was very together and very quick on The Big Breakfast and that's exactly what's required Chris Tarrant (right) on Johnny Vaughan

Vaughan, who will start his new job in March, said he was "thrilled to bits".

"Almost from the day I had to leave The Big Breakfast, I really missed the buzz of doing something live each day," he said.

"I think when you look at a breakfast DJ they are more in touch with their audience than anyone else. They have got to go to work and so do the audience and the listeners can feel that."

Tarrant, 56, said of his replacement: "He was very together and very quick on The Big Breakfast and that's exactly what's required for the breakfast show, as well as being able to get out of bed."

Surprised

He added that he was surprised the BBC's contract with Vaughan allowed him to work for a commercial rival.

"I didn't think we could get him away from the BBC - I thought they would have tied him up with one of those bi-media deals," he said.

"They should have done and I suspect that if they had got a whiff of this they would have done."

Tarrant said he was pleased the "ridiculous" speculation about his future was coming to an end - and explained he was hoping to wind down his broadcasting commitments over the next few years.