Labour contender: Diane Abbott
When Diane Abbott announced on BBC Radio 4's Today programme that she planned to stand for the leadership of the Labour Party, some at Westminster wondered if she was being serious.
It was such an unexpected announcement, from someone who had never held a job in government and who, though not lacking in ability, had apparently settled for the life of the rebellious backbencher and left wing thorn in the side of New Labour.
She had also carved out an alternative career as a TV pundit, sharing a late night sofa with old school friend Michael Portillo on BBC One's This Week.
When questioned about her surprise decision, she simply said: "If not now when? If not me who?"
There was certainly an audible sigh of relief from the Labour Party, which was acutely aware of how it looked to voters to have four white, middle class, former New Labour special advisers in their early 40s battling it out for the top job in a party that is meant to value diversity.
Front-runner David Miliband even nominated her to help ensure she got enough support from MPs to get on to the ballot paper, saying he wanted to ensure the left had a voice in the debate which would shape the party's future.
She was also helped by the withdrawal of fellow left-winger John McDonnell.
There were mutterings from some that she was simply there to make up the numbers, as a token nod to cultural diversity and the Labour left.
But as the contenders embarked on an endless series of hustings around the country, she proved her worth to the debate, shattering the cosy, fraternal atmosphere, with some well-aimed barbs at her four rivals, who she has dubbed "geeky young men in suits".
She also managed to steer the debate away from blaming Labour's election defeat on its immigration policy, which David Miliband and others had initially been suggesting, by stressing that it was other factors, such as jobs, housing and wages, that mattered more to voters in Labour's heartlands.
Miss Abbott - who in 1987 became Britain's first black woman MP - sees herself as a trailblazer and has spoken of her disappointment at how few women from ethnic minorities have followed her into the Commons.
Born in London in 1953, the daughter of West Indian immigrants, Diane Abbott attended Harrow County grammar school, where she acted in a play opposite Michael Portillo, was was later to become a leading Conservative.
After school, she went on on to Newnham College, Cambridge, graduating with a history degree.
She then worked at the Home Office, followed by a stint as a civil liberties campaigner and some time as a breakfast TV reporter, before becoming an MP.
She claims to be the best placed of the five leadership candidates to rebuild the Labour Party, as she knows it the best and has not been "fast tracked" to the top of the party or "parachuted in" - another dig at her rivals. She doubled her vote at the 2010 general election in Hackney North and Stoke Newington.
She has tried to turn what could be seen as a drawback - her lack of experience in government - to her advantage by accusing the "boys", as she calls them, of being "up to their necks" in the bitter feuding of the Blair and Brown era and of using hustings events to disown key policy decisions made at the time.
"You would not believe, to hear them, that they were at heart of the New Labour project for at least a decade," she told BBC News.
She said she had been the most "consistent" of all the candidates on policy.
"I have not discovered in the past couple of months that I was against the Iraq war."
Her campaign website - by far the most eyecatching of the five contenders - stresses the point that she offers something different.
And although she has been careful not to pigeonhole herself solely as a candidate of the left, her policy platform is by the far most traditionally left wing of the five contenders, as you would expect.
She has called for big increases in taxes - including a new "wealth tax" - so action to tackle Britain's budget deficit is 50% from spending cuts and 50% tax rises rather than 80% cuts/20% tax rises planned by the coalition.
She has also called for the plans for a replacement for the Trident nuclear weapon system to be scrapped, and has campaigned against higher tuition fees.
But there has also been controversy.
Long branded a hypocrite by fellow left-wingers for sending her son to a private school, she provoked a further storm of protest when she explained her decision last month by saying: "West Indian mothers will go to the wall for their children."
It led to her being accused of "racism" against white people by her old sparring partner Andrew Neil in a This Week interview, during which she repeatedly batted away his questions with the line: "Andrew, I have nothing new to say."
It was a jarring note in a campaign which began on a wave of media goodwill - The Guardian headlined one piece "Go Diane" - and had seen her pick up backing from two trade unions and nine local constituency parties by mid-July.
If she managed to pull off the seemingly impossible in September and win the leadership, it would be one of the biggest upsets British politics has seen, representing the beginning of a new chapter in the history of the Labour Party, and possibly, the country.
But even if she finishes last, with a creditable share of the vote, she could find herself playing an unexpectedly central role in the future of the Labour Party, perhaps as a member of the shadow cabinet - something few would have dared to predict before that Today interview back in May.