Ken Livingstone is the rebel who became part of the establishment.
In the 1980s, during his first reign over London, he was a left-wing firebrand who was almost as much of a thorn in the side of Labour's leadership as he was for Margaret Thatcher.
Two decades later, he defied Tony Blair's New Labour to win the newly-created position of London mayor.
But now he is in new political territory, no longer the maverick but the party's official candidate for the second time running, with Gordon Brown among those joining him on the campaign trail.
Kenneth Robert Livingstone, 62, was born in Lambeth, south London, at the end of the Second World War.
He went to Tulse Hill Comprehensive School before training as a teacher, then becoming a technician for a cancer research institute.
He joined the Labour Party in 1969 and went on to become a Labour councillor in Lambeth.
He led the Greater London Council during the turbulent years of the early 1980s, famously goading Mrs Thatcher across the Thames in Parliament by hanging a banner from County Hall with the unemployment figure on it.
At the GLC, `Red Ken' became a bete noire of the right, supporting everyone from striking miners to Sinn Fein's leaders at the height of the IRA's bombing campaign.
After the Tories abolished the GLC in 1986, Mr Livingstone crossed the Thames, becoming MP for Brent East a year later.
At Westminster, he joined the ranks of Labour's left wing MPs, harrying the Tories but also clashing frequently with his own party's modernisers.
He had a fraught relationship with the New Labour leadership and was expelled from the party for standing for Mayor as an independent in 2000 after Tony Blair opposed his candidature.
Relations slowly improved as he established himself as Mayor and he was gradually welcomed back to the Labour fold.
Mr Livingstone is running for a third term on his record.
There was widespread praise for the way he stood up for London after the July 2005 suicide bombings.
He can also boast of the introduction of the congestion charge, increases in bus services, the 2012 Olympics and getting the organisers of the Tour de France to start last year's race in London.
But his reign as London mayor has been no less controversial than any other time in his career.
He found himself in hot water in 2005 when he likened a Jewish reporter to a Nazi concentration camp guard.
A High Court judge later ruled that he had not brought his job into disrepute by doing so but that he had been "unnecessarily offensive".
He also said Jewish billionaires David and Simon Reuben could ``go back to Iran and try their luck with the ayatollahs'' in March 2006 during a row over the development of the 2012 Olympic site in east London, in which the brothers held a 50% stake.
More recently, with Mr Livingstone's third election campaign looming, one of his closest aides, Lee Japser, was suspended then resigned amid allegations about the use of public funds.
Copyright P.A.
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