Boris reignites tension with Cameron by admitting 'I would love to be Prime Minister'

The London mayor made his remarks as he prepared to receive the Olympic flag in Beijing.

It was the third time in less than a week that he has alluded to a political future as leader of the Conservative Party.

Last Tuesday, Mr Johnson risked irritating Mr Cameron by dismissing his 'broken society' message as 'piffle'.

Boris Johnson has compared himself to Roman leader Lucias Quinctius Cincinnatus who led his people to victory

Three days later he said he 'could not foresee the circumstances' in which he would become top Tory  -  the exact form of words Michael Heseltine used about challenging Margaret Thatcher, months before he did so.

Yesterday, Mr Johnson was asked during a press conference if he would one day like to become Prime Minister.

Grinning, he said: 'I wish I could think of a way of encouraging that kind of speculation but I can't.'

A moment later, however, he added: 'Were I to be pulled like Cincinnatus from my plough, then obviously it would be a great privilege.'

Mr Johnson was referring to Lucius Quinctius Cincinnatus, a noble Roman consul who left politics in about 460BC to return to work on his small family farm.

Years later, when the Roman army was surrounded by hordes of warring tribesman, a group of senators was sent to tell him that he had been nominated as dictator.

Cincinnatus was found ploughing his field, but he agreed to return to Rome and led his new army to victory.

Afterwards, he gave up power voluntarily and went back to the land.

Mr Johnson, who makes a habit of quoting from the Classics, is often portrayed as a 'bumbling buffoon' but he has a ferocious intellect and has never hidden his desire to be leader of the Tory Party.

The rivalry with Mr Cameron dates back to Eton and Oxford, where they were acquaintances.

Mr Johnson is supposedly more intellectually gifted but Mr Cameron earned a First that his colleague missed out on.