Three years ago Sir Keir Starmer seriously considered throwing in the towel after seeing Labour crash to a humiliating defeat in the Hartlepool by-election.
A little more than a year into the job as party leader, even allies were questioning whether he had what it took to return them to power after the Tories romped home in the formerly safe Labour stronghold.
The setback was compounded by a series of losses in council elections taking place in England the same day.
The Blairite former minister Lord Adonis suggested he was no more than a “transitional figure” without the “political skills” needed to make it to the top while critics on the left were openly gloating.
Badly bruised by the result, having made repeated visits to campaign in the constituency – “I felt like I had been kicked in the guts” – he told aides that it was a “personal rejection” and he had to go.
In his hour of darkness, his wife, Victoria, was among those who rallied round and persuaded him to carry on.
Having pulled round from that “near-death experience”, and dragged his party back to the brink of electability in the process, he is now preparing for the final push that could see him become the UK’s next prime minister.
But while his trademark grey quiff has become a fixture at Prime Minister’s Questions, he remains in the eyes of many voters an unknown quantity who has yet to define what he truly stands for.
An avid football fan – he is an Arsenal season ticket holder – he may now be challenging for the top honours, but like the team he supports he has struggled to shed the “boring” tag.
A one-time “lefty lawyer” from north London, he has been depicted by opponents as the epitome of a self-satisfied liberal metropolitan elite, remote from the concerns of ordinary voters.
However he grew up in very different circumstances sharing a cramped, ramshackle “pebble-dash semi” with three siblings and a mother who was seriously ill for much of his childhood.
When he stood for leader in the aftermath of Labour’s crushing 2019 general election defeat, he ran on a leftish platform with commitments to renationalise water and energy and scrapping university tuition fees.
He has since been accused of systematically abandoning his principles, dropping key policies one by one, as he has tacked steadily to the right.
To his supporters, he is a pragmatist utterly focused on taking Labour back to power, believing real change cannot be achieved from the impotence of opposition.
And while some on the left have cried betrayal, his critics in the party have been largely sidelined as it recovered to establish a commanding lead in the opinion polls.
A late entrant to politics after a high-flying legal career – including a five-year stint as director of public prosecutions – Sir Keir has seemed to some too “lawyerly” and buttoned up to connect with voters.
His friends insist that such a characterisation is unfair, saying that in private he is warm and engaging, whether propping up the bar, pint in hand, at his local or cooking a meal at home with his family.
A recent biography by journalist and former Labour spin doctor Tom Baldwin cast new light on his apparent reticence in public, describing a difficult childhood growing up in straitened circumstances in the Surrey commuter-belt town of Oxted.
Named after the first Labour leader, Keir Hardie, his father, Rodney, was a toolmaker and his mother, Jo, an NHS nurse who suffered from a rare condition which left her with a debilitating form of rheumatoid arthritis normally associated with someone much older.
In constant pain, it meant that for much of his childhood she was in and out of hospital – an experience that was to have a profound effect on him.
At the same time his younger brother, Nick, suffered from learning difficulties, leading to fights at school as Keir and his sisters sought to defend him from bullies.
His father meanwhile was a distant, uncommunicative figure who banned the children from listening to pop music or watching TV shows such as Tiswas or Starsky And Hutch and who hated Margaret Thatcher.
It was only after Rodney died and he discovered a scrapbook of press cuttings he kept chronicling his career that the adult Sir Keir finally understood the pride his father had taken in his achievements.
Difficulties at home did not stop him doing well at school – passing the 11-plus to gain a place at Reigate Grammar School, while his prowess at sport and music earned him the nickname “Superboy” from his siblings.
Determined to break away from his small town background, he won a place at Leeds studying law – a course chosen largely to please his parents – making him the first member of his family to go university.
He drove there in a battered Morris Minor, paid for by a summer spent “punching holes in metal” for his father.
He was at times uncomfortable in his new surrounds – while fellow students talked knowledgeably about which branch of the profession they hoped to follow, he realised he had never even met a lawyer and had little idea of what they did.
Typically he responded by simply working harder than anyone else, his efforts being rewarded with a first honours and a place at Oxford on a postgraduate degree course in civil law.
He was also becoming increasingly involved in politics, helping run Socialist Alternatives, an obscure Trotskyite magazine, and writing articles earnestly proclaiming Karl Marx was “of course” right over the way to achieve real societal change.
After being called to the bar in 1987, three years later he was among an idealistic group of progressive lawyers who formed the Doughty Street chambers, specialising in human rights with half their cases either paid for by legal aid or free of charge.
Mr Starmer, as he then still was, was soon involved in advising the so-called McLibel Two, a pair of environmental activists who famously took on McDonald’s in a marathon David v Goliath defamation case.
He also made repeated trips to Commonwealth countries in the Caribbean and Africa to represent defendants facing the death penalty, work which helped win him a “QC of the year” award, and drew up legal arguments against the Blair government’s 2005 invasion of Iraq.
At the same time, he belied the conventional “lefty lawyer” image by serving as an adviser to the Association of Chief Police Officers and newly formed Northern Ireland Policing Board, and in 2008 he was appointed director of public prosecutions.
The Tories are reported to have compiled a dossier on his time at the Crown Prosecution Service with a view to embarrassing him during the election campaign, although his supporters remain confident he has nothing to fear.
In 2022 Boris Johnson was forced to row back on a claim that Sir Keir failed to prosecute Jimmy Savile for child sex abuse after even some Tories were angered at the then prime minister’s attempt to make political capital of the issue.
Among the notable decisions he was involved in were the charging of cabinet minister Chris Huhne for seeking to evade speeding points and the fast-track prosecutions of offenders following the 2011 riots in London and other English cities.
It was only after his term of office – for which he was awarded a knighthood – came to an end in 2013 that he turned seriously to politics.
In 2015 he was elected MP for the safe Labour seat of Holborn and St Pancras only to see the party suffer its second general election defeat in a row.
He was made a shadow home office minister by new leader Jeremy Corbyn, but was among a wave of frontbenchers to resign in the wake of the tumultuous aftermath of the 2016 referendum vote to leave the EU.
After Mr Corbyn saw off the ensuing leadership challenge, Sir Keir – an ardent Remainer – agreed to return to the fold as shadow Brexit secretary.
Pressed subsequently by Tories about why he had done so when he had discarded so much of Mr Corbyn’s left-wing agenda, he claimed he had a duty to help mitigate the effects of withdrawal, fighting to keep open the option of a second referendum.
Not all were convinced by such arguments, but his stance did nothing to damage his prospects within the party.
Following Mr Corbyn’s resignation after leading Labour to its worst result in more than 80 years in the 2019 election – fought on Mr Johnson’s pledge to “get Brexit done” – Sir Keir quickly emerged as the overwhelming favourite to replace him.
One of his first pledges on being elected leader was to rid the party of the “stain” of antisemitism which had taken hold under his predecessor.
He soon revealed a ruthless streak when Mr Corbyn complained that a damning report by the Equality and Human Rights Commission had overstated the problem by sacking him from the Parliamentary Labour Party – an ultimate act of distancing.
His start as Labour leader was overshadowed by the Covid pandemic while the party’s rise in the polls has owed much to the Tories’ implosion, first with Mr Johnson and the “partygate” scandal and then Liz Truss’s calamitous whirlwind premiership.
His allies however insist that credit must also go to his forensic examination of Mr Johnson’s handling of the pandemic and the reassurance he was able to offer in response to the financial chaos created by Ms Truss.
After the nadir of Hartlepool, he has systematically strengthened his grip, with a string of by-election victories while steadily moving to claim the political centre ground, promoting a clutch of Blairites in last year’s shadow cabinet reshuffle.
His hold over the party was underlined by the relatively muted response to his decision finally to drop a flagship £28 billion “green” investment pledge, seen as too easy a target for Tory claims of Labour fiscal profligacy.
If that seemed to some overly cautious, the biggest challenge he has had to face in recent months has come from the war in Gaza, which prompted a series of frontbench sackings and dismissals over his reluctance to call for an immediate ceasefire.
Away from Westminster, Sir Keir’s passion for football runs deep: at the age of 61 he continues to organise and play in regular eight-a-side matches with a group of old north London friends.
On the pitch, he is described as a highly competitive, box-to-box, midfield dynamo: his supporters will be hoping that he has the drive to propel him all the way to No 10.
