Mayor Johnson 'would like to be PM'

London Mayor Boris Johnson has admitted that he would like to be prime minister - but he insisted "it's not going to happen".

The politician, 48, who has been seen as a possible future rival to David Cameron, said he would want to "have a crack" at the job "if the ball came loose from the back of a scrum".

He was asked whether he harboured ambitions for the top job in British politics in a forthcoming BBC Two documentary.

Michael Cockerell, who made the programme, told the Radio Times that Mr Johnson answered: "I would like to be the lead singer of an international rock group. That was my aim, or a good guitarist.

"I would love to have been a world-famous painter or a composer. There are many things that I would like to have been able to do."

When the documentary-maker pressed him again, he replied: "I think it's a very tough job being prime minister.

"Obviously, if the ball came loose from the back of a scrum - which it won't - it would be a great, great thing to have a crack at. But it's not going to happen."

Mr Johnson's sister Rachel said the mayor, who at the age of 12 painted a self-portrait resembling a Grecian demi-god according to the documentary-maker, set his sights high when he was a child.

"As Boris was growing up whenever anyone asked him what he wanted to be, he would answer - 'World King'," she said.

She said of her brother's current relationship with the Prime Minister, with whom he went to school at Eton: "When they're together it's rather sweet, because David Cameron - even though he's taller - looks at Boris as if he's still head boy at Eton. Remember, Cameron was two years younger - the young pup."