For more than four decades Ken Livingstone has been a figurehead of the Labour left - and something of a hate figure for much of the rest of the political establishment.
In his heyday, "Red Ken" was a thorn in the side both of Margaret Thatcher's Tories and New Labour under Tony Blair.
In their efforts to thwart him, the Conservatives resorted to legislation to end his reign at the Greater London Council, while Labour was so determined to prevent him becoming London mayor it stitched up the selection process, to disastrous effect.
But his time in the party has ended ignominiously, as he quit amid furious demands for his removal over allegations of anti-Semitism.
Mr Livingstone first began to blaze a trail through London politics in the early 1970s.
Within two years of joining the Labour Party in 1969, Mr Livingstone was elected as a councillor in his native Lambeth in south London in 1971 before joining the Greater London Council in 1974.
He 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.
He famously goaded Mrs Thatcher across the Thames in Parliament during the turbulent 1980s by displaying the unemployment figures on City Hall.
After she secured revenge by abolishing the GLC, he joined the ranks of Labour's left-wing MPs as member for Brent East from 1987-2001, harrying the Tories but also clashing frequently with the New Labour modernisers.
When Tony Blair restored devolved government to the capital and created the powerful post of mayor he certainly did not anticipate that it would open the door for his foe's return.
But every attempt to prevent his worst-case scenario backfired, as Mr Livingstone stood as an independent against official Labour candidate Frank Dobson in 2000 and won.
Such was Mr Livingstone's popularity that Mr Blair was forced to welcome him back into the fold and ensure he was the official Labour candidate in 2004.
During that second term, Mr Livingstone won widespread praise for the way he stood up for London after the July 2005 suicide bombings and he helped win the 2012 Olympic Games for the capital.
However he also became embroiled in a series of disputes with sections of the capital's Jewish community, leading to allegations of anti-Semitism.
In 2006 a High Court judge said he made "unnecessarily offensive" and "indefensible" remarks likening a Jewish reporter to a Nazi concentration camp guard.
He was however cleared of bringing the office of mayor into disrepute, a ruling he hailed "victory for democracy and common sense".
His time in office was ended in 2008 when he was defeated by an equally maverick and colourful opponent in Boris Johnson and a failed bid to return to City Hall in 2012 marked the end of his electoral ambitions.
The election of Jeremy Corbyn as Labour leader in 2015 appeared to have given him a fresh leash of life politically, as he enthusiastically backed the policies of his old ally on the left.
However he found himself at the centre of new storm the following year when he came to the defence of MP Naz Shah who had been suspended over offensive social media posts.
Mr Livingstone insisted that while her remarks were "over the top", she was not anti-Semitic, and that he had never encountered anti-Semitism in 40 years in the Labour Party.
He then sparked fury by going on to claim in a radio interview that Hitler "was supporting Zionism before he went mad and ended up killing six million Jews".
Despite being suspended by the party, he insisted he stood by the comments which he said referred to an agreement in 1933 between the Nazis and some German Zionists to resettle Jews in Palestine.
He caused further anger by talking about "collaboration" between the Nazis and Zionists.
After the protest against anti-Semitism outside Parliament in March, campaigners demanded should his permanent expulsion as proof the Labour leadership was serious about dealing with the issue.