Profile: Ken Livingstone, fails in last campaign

Ken Livingstone has bowed out of electoral politics after more than four decades, announcing that his unsuccessful fourth tilt for London mayor was his last election.

Exactly four years ago, Ken Livingstone's political obituary was penned by many pundits after Boris Johnson dramatically brought to an end his eight-year reign at City Hall.

Reports of his demise proved as exaggerated as Mark Twain's: within two years he had not only secured the Labour candidacy for a fourth tilt but appeared well-set to return in triumph.

But a seasoned campaigner famous for defying the odds proved unable to win even when they were stacked in his favour - neither his personal nor political magic working on Londoners.

And his defeat by the wafer-thin margin of 48.5% - 51.5% to Mr Johnson prompted an immediate announcement of his decision not to stand again.

Even before his announcement, it was impossible to imagine Labour - the party which once begged him to return to the fold - would ever again invest in Mr Livingstone, 66, as the answer to its prayers in the capital.

As his campaign unravelled - in the main thanks to controversy over his personal taxes - high-profile Labour figures lined up to express regrets at his return and tell voters not to back him.

Such was the poisoned atmosphere that Labour election chief Tom Watson went so far as to say that voters should "hold their noses" and vote for his own party's candidate.

That was a sentiment echoed by an eve-of-poll editorial in The Guardian.

In Mr Livingstone's heyday he was the left-wing thorn in the side of the Tories - Margaret Thatcher resorted to legislation to remove him in 1986 - as well as of Tony Blair's government, which was so determined to exclude him that it stitched up the selection process, to disastrous effect.

But he 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.

Soon known as "Red" Ken, 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 hanging a banner from County Hall with the unemployment figure on it.

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 Mr 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 his 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 helped win the 2012 Olympic Games for the capital.

There were a string of popular policies too - though tempered by the sorts of personal and professional controversies that have followed him throughout his career.

In 2005 he narrowly avoided serious punishment when he likened a Jewish reporter to a Nazi concentration camp guard - a theme that also dogged this most recent campaign.

A close aide was forced to quit over claims he misused public funds and Mr Livingstone's unusual private life, involving five children by three partners, was the subject of intense scrutiny.

Despite that - and the dismal opinion poll ratings of Gordon Brown's unpopular Labour government - he may have clung on but for an equally maverick and colourful opponent in Mr Johnson.

With the roles almost exactly reversed four years on, for some time it looked possible that Mr Livingstone could cut short the Tory's tenure.

But his momentum was dramatically arrested by a row over claims he set up his business affairs to avoid paying large sums in income tax - and his refusal to publish accounts in full.

A bitter personal battle between the two main rivals ensued - one which the results demonstrate was won by the incumbent.

As he contemplates defeat, Mr Livingstone will be a spectator rather than a key participant for the London Olympics he helped secure.

And he will be a spectator too when the contenders next line up for the race for the mayoralty. Just don't expect him to be a quiet one.