By Brian Wheeler
Political reporter, BBC News
Has there even been a more enigmatic politician than Gordon Brown?
No-one has ever doubted the formidable intellect and iron determination of Britain's new prime minister.
Born: 20 February 1951
Educated: Kirkcaldy High School, Edinburgh University
Family: Married, two sons (daughter died shortly after birth)
1972: Rector, Edinburgh University
1975: Temporary lecturer
1976: Politics lecturer, Glasgow College of Technology
1980: Television journalist, STV current affairs
1983: Labour MP, Dunfermline East
1985: Opposition front bench trade and industry spokesman
1987: Shadow chief secretary to the Treasury
1989: Shadow trade and industry spokesman
1992: Shadow chancellor
He was marked out as gifted from an early age, although he resented it at the time, and seemed to excel at everything he tried, rising rapidly through the ranks of the Labour Party and inspiring fierce loyalty in those close to him.
Yet the abiding public image of Gordon Brown is of a dour, self-absorbed figure, a "control freak", who has spent more than a decade coveting the job of his more charismatic Downing Street neighbour.
This is entirely at odds with the warm generous and engaging character described by Mr Brown's family and friends.
So who is the real Gordon Brown? And what is there in his background to explain the extraordinary drive and determination that has been the hallmark of his near 40 year career in politics?
James Gordon Brown was born in February 1951, the second son of Rev Dr John Ebenezer Brown, a Church of Scotland minister.
The family lived in Glasgow until Gordon was three, when they moved to Kirkcaldy, a small industrial town on the northern shore of the Firth of Forth and the area he represents in Parliament today.
Gordon was the shyest of the Brown boys, his mother said
Mr Brown has often said his parents were the "inspiration" for his career in politics and the source of his "moral compass".
Kirkcaldy was going through tough times in the 1950s and the Brown brothers, Andrew, Gordon and John, were encouraged to help local families made unemployed by factory closures.
Africa was also an early concern. Inspired by one of their father's sermons, Gordon and his older brother John set up a tuck shop in the family's garage and started a newspaper, The Gazette, to raise money for refugees.
Gordon - who was mad about football and sold programmes at Raith Rovers on Saturdays in exchange for free entry to games - was The Gazette's sports editor.
But the paper also provided an early platform for his views on politics and society. In one article, he backed a church campaign against the evils of alcohol and tobacco.
His mother Elizabeth described him as "the shyest member of the family" but he excelled at sport and school friends remember him always being at the centre of things.
His political affiliations were never in doubt. By the age of 12 he was pushing Labour Party leaflets through letterboxes in Kirkcaldy.
He was also academically gifted. After sitting an IQ test, he was sent to Kirkcaldy High School at the age of 10, where he and fellow members of the "e-stream" were taught in separate classes as part of an experiment in academic fast-tracking.
Brown sat his Highers, the Scottish equivalent of A-levels, two years early and was named the "Dux", or leading scholar of his year.
But he appears to have resented being separated from his age group and angry that some of his e-stream friends had been pushed to breaking point in pursuit of academic success.
In an unpublished 1967 essay, he describes himself the "victim of a totally unsighted and ludicrous experiment in education, the result of which was to harm materially and mentally the guinea-pigs".
At the age of 16, he had joined his older brother John at Edinburgh University, the youngest fresher there since 1945.
But disaster struck in his first week of term when he was diagnosed with a detached retina - thought to be the result of being kicked in the head during an end of term rugby match at Kirkcaldy High.
He missed the entire first term while doctors battled to save his sight. He would be in and out of hospital for the next five years, often spending weeks lying on his back in a darkened room. He eventually lost the sight in one eye and retained just 30% of his vision in the other.
Edinburgh university was the launchpad for Brown's political career (PIC: STV)
The experience appears to have had a profound effect on Brown.
"It made him more determined,'' his older brother John recently told The Daily Telegraph.
"He was in more of a hurry; he feared he might lose his sight altogether. It was a bleak time.''
Edinburgh University in the late 1960s was a hotbed of student radicalism and Brown made sure he was in the thick of it.
Brown became an MP at a torrid time for Labour
In his second year he followed in the footsteps of his older brother by becoming the editor of The Student magazine, grabbing national headlines by exposing the university's investments in pro-apartheid South Africa.
Then, after graduating, with a first, he launched a campaign to be the university's Rector.
This was traditionally an honorific post, normally going to a showbusiness personality.
But it came with a rarely exercised legal right to chair the university's governing body - something that proved irresistible to 20-year-old Brown's anti-establishment instincts.
He swept to power with a campaign boosted by three mini-skirted fans, The Brown Sugars, who accompanied him to photo opportunities in "Gordon for me" T-shirts.
And he wasted no time in becoming a thorn in the side of the university authorities, successfully fighting a court battle with them when they tried to overturn his election.
Edith Cavell, nursed World War One wounded in Belgium
Dietrich Bonhoeffer, Protestant pastor who led German opposition against the Nazis
Raoul Wallenberg, businessman who tried to save Hungarian Jews in 1944
Martin Luther King, US civil rights leader
Robert Kennedy, John F Kennedy's brother
Nelson Mandela, South African civil rights leader
Dame Cicely Saunders, founder of hospice movement
Aung San Suu Kyi
, led opposition to dictatorship under house arrest in Rangoon
Source: Courage: Eight Portraits, by Gordon Brown, Bloomsbury publishing
Officials' irritation at his publicity-seeking antics is evident from one internal memo written by the university's information officer.
"The Rector appears to be sensitive to the fact that the BBC did not contact him yesterday to appear on television," the officer writes.
"I told him this was a matter for the BBC to decide whether or not they should follow up any story. In confidence I have warned the BBC News Editor in Edinburgh about the Rector's attitude."
When his three-year term ended, Brown even tried to get the authorities to declare the day a special academic holiday, with no lectures or classes.
"He was a big star and had a natural way with people," radio presenter Simon Pia, who was taught by Brown during this period, would later recall.
"He would hold his tutorials in his flat over a couple of cans of beer. He held all sorts of parties. He had loads of friends from all different backgrounds.
"People were diving into bedrooms and smoking joints. He never indulged, but there was nothing disapproving about him either.''
'Madly in love'
Brown cut an untidy figure about campus, with his notes invariably stuffed into Marks and Spencer carrier bags, but he had no shortage of female admirers.
He even enjoyed an unlikely romance with an exiled Romanian Princess, who was studying at the university.
Brown was a rising star in the Scottish Labour party
Margarita du Romaine was a god-daughter of the University's Chancellor, Prince Philip and 81st in line to the British throne.
She fell "madly in love" with Brown, she would later recall, and moved into his digs in Marchmont Street.
But Brown's growing obsession with politics appears to have killed off their relationship, with Princess Margarita reportedly complaining after they had split up that it was "politics, politics, politics" with Brown - he had no time left for her.
By now, he was lecturing in politics at Glasgow College of Technology and well on his way to becoming a major figure in the Scottish Labour Party.
At the age of 23, he nearly became a candidate in the second general election of 1974.
He was also working on a thesis on maverick 1930s MP James Maxton, the "Red Clydesider", which he would later turn into a book.
The 1997 Budget set the tone for Brown's decade at the Treasury
In 1975, he made a big splash with The Red Paper for Scotland, a collection of essays on the country's political future, in which he called for "a positive commitment to creating a socialist society".
He fought Edinburgh South for Labour at the 1979 general election, narrowly losing out to future Conservative minister Michael Ancram.
Then, after a spell as a television journalist and producer for STV in Glasgow, he won the safe Labour seat of Dunfermline East, at the 1983 general election, at the age of 32.
A few weeks after entering the Commons, Brown began sharing an office with another new boy, Tony Blair, a 30-year-old Islington barrister.
It was a grim time for Labour, which had just slumped to its lowest share of the vote in 60 years and was haemorrhaging support to the newly-formed Social Democratic Party.
The new chancellor had little time for the traditions of the City
Brown and Blair shared a sense of frustration at Labour's direction and the left-wing faction fighting that was tearing the party apart.
They were both convinced Labour had to change if it was ever going to win power again and they quickly became inseparable - bouncing ideas off each other, going on foreign trips together, even writing each other's speeches.
Brown was very much the senior partner. He was two years older than Blair, seen as more of an intellectual heavyweight, with deeper roots in the Labour movement.
He tutored Blair in how to handle the media, using his television experience to craft snappy soundbites and eye-catching press releases.
The pair's potential was spotted by Labour leader Neil Kinnock who promoted them into his shadow cabinet.
They were soon joined in their mission to modernise the party - and shake-up its communications strategy - by Peter Mandelson, a former TV producer hired by Kinnock to be his media chief.
The relationship that came to dominate British politics
By the early 1990s, Brown was riding high. When Kinnock allowed him to stand in for shadow chancellor John Smith after his first heart attack, he dazzled Labour MPs with his demolition of the Tories at the despatch box.
His popularity with Labour members was at its height and he regularly topped shadow cabinet elections.
But when Smith died of a second heart attack in 1994, Blair and Brown found themselves pitted against each other as rivals for the party leadership.
Mandelson had become convinced it was Blair, the smiling family man with the middle-class background, who would most appeal to swing voters.
A much commented on, but never explicitly confirmed, deal was eventually struck between Blair and Brown over dinner at Islington's Granita restaurant.
In exchange for giving him a clear run at the leadership, Mr Blair promised he would make Brown the most powerful chancellor in history, with unprecedented control over domestic policy.
The terms of the deal remain hotly contested, creating a tension at the heart of New Labour that would dominate politics for more than a decade.
Brown believed he had been manoeuvred out of the leadership and has never appeared to have forgiven his former ally Peter Mandelson for what he regarded as betrayal.
But the goal that united them all in the 1990s was to get Labour into power after 18 years in opposition.
Together they formed a hugely effective campaigning machine, and no one worked harder than Gordon Brown to secure the 1997 election victory that saw Tony Blair swept to power with a landslide.
He would put in 18 hour days, often ending up at the Park Lane apartment of millionaire Labour MP Geoffrey Robinson, who would become his first pay-master general, talking tactics and swapping political gossip with his closest advisers, economist Ed Balls and spin doctor Charlie Whelan.
Whelan even tried to transform Brown's dour image, encouraging him to smile more on television.
But personality politics was not something that came easily to Brown.
His reluctance to talk about his private life even sparked rumours he was gay.
In fact, he had enjoyed on-off relationships with TV journalist Sheena Macdonald and Edinburgh lawyer Marion Caldwell since splitting up with Princess Margarita and, by 1995, was dating PR executive Sarah Macauley.
As Blair entered Downing Street on a wave of public optimism, Brown swung into action at The Treasury, granting control of interest rates to the Bank of England and freezing public spending for two years.
The Browns' wedding was a characteristically modest affair
Brown set about annexing powers from other departments, as he extended the reach of The Treasury into nearly every area of domestic policy.
Requests for more cash from ministerial colleagues were met with stern refusals, with little room for debate or discussion.
Decisions that might ordinarily have been expected to be made by a prime minister were being made at the Treasury.
Lord Turnbull, Brown's former permanent secretary, has since marvelled at the "Stalinist ruthlessness" of his negotiating style: "His view is that it is just not worth it and 'they will get what I decide'."
The power Brown held over vast areas of domestic policy led to fractious relations between No 10 and the Treasury.
As early as January 1998, unnamed Blair allies had briefed a newspaper about Mr Brown's alleged "psychological flaws," after he sanctioned the publication of a biography suggesting Mr Blair had cheated him out of the Labour leadership.
Blair allies would complain that the chancellor would keep the details of his Budgets from Mr Blair until the last possible moment and "go missing" when the prime minister needed his public support.
But the biggest flashpoint in Labour's first term was over the euro.
Blair saw it as his destiny to take Britain into the single European currency but Brown, who was less enthusiastic, managed to seize control of the policy.
He turned it into an economic - rather than a political - decision by announcing five economic tests which had to be passed before he would recommend that the issue should be put to a public referendum. He would later hail it as one of his best decisions.
Family life transformed Brown's image
After the 2001 general election, relations between the Treasury and Number 10 reportedly deteriorated further.
Mr Blair's former EU adviser Stephen Wall recently told a Channel 4 documentary there was a "constant battle" between the two rival power bases, with Treasury staff regarding contact with Downing Street as "a kiss of death for their careers".
Matthew Taylor, Mr Blair's former policy chief, said staff felt like "children in a dysfunctional relationship where mum and dad are too busy arguing to ever talk to the kids".
Whenever things got out of hand, Deputy Prime Minister John Prescott would host a reconciliation dinner with Blair and Brown at his grace and favour apartment at Admiralty Arch.
Brown was, by now, a married man with a young family of his own.
His relationship with Sarah Macauley had been reluctantly dragged into the light, at Charlie Whelan's prompting, on the eve of his first Budget in 1997, when the couple agreed to be photographed dining together by The News of the World.
But it was another three years before they finally tied the knot, in a modest ceremony in the living room of Mr Brown's North Queensferry home, witnessed by their families and a few close friends.
A more relaxed Brown promises to 'listen and learn'
They honeymooned in Cape Cod, Mr Brown's favourite summer holiday destination, their typically frugal economy class seat being upgraded courtesy of Virgin Atlantic.
The following year, 2001, the Browns became parents, with the premature birth by Caesarean section of Jennifer Jane, weighing 2lb 4oz.
But tragedy struck just 10 days later when the little girl suffered a brain haemorrhage and lost her fight for life in her parents' arms at Edinburgh Royal Infirmary.
When, two years later, the couple had a son, John, the normally reserved Brown could barely contain his joy as he presented the little boy to waiting photographers at Edinburgh's Royal Infirmary.
For once, he did not have to be reminded to smile for the cameras.
In July 2006, the Browns had a second son, James Fraser, diagnosed four months later with cystic fibrosis.
Brown's image as an workaholic bachelor, with no time for anything but politics, has been transformed by becoming a family man.
Brown launched his leadership bid with a pledge to be 'humble'
Friends say the couple are well-suited and Brown has become more relaxed and outgoing - more likely to talk about what John or Fraser have been up to than the details of the latest government spending review.
Politically, Brown achieved what many had thought impossible and gave Labour a reputation for sound economic management.
It allowed him to unveil large increases in public spending paid for, in part, by tax increases, prompting accusations from the opposition that he was increasing tax by "stealth".
But by 2003, he was coming under increasing pressure from his own allies, frustrated at his apparent reluctance to move in for the kill over the leadership.
At that year's Labour conference, he made what was widely interpreted as the opening salvo of a leadership campaign - with a speech appealing to the party's "soul" telling activists "we are best when we are Labour".
His moment seemed to have arrived the following January when Mr Blair - weakened by a public backlash against the Iraq war - faced a crunch Commons vote on university top-up fees.
The prime minister would almost certainly have had to resign if he had lost.
But although he reportedly kept Blair guessing until hours before the vote, Brown eventually instructed his supporters, through loyal lieutenant Nick Brown, to swing behind the government, helping Blair win by a margin of just five votes.
Brown secures an exit date - and prompts criticism from Blairites
According to some accounts, Nick Brown had tears in his eyes as the chancellor told him to back top-up fees - a policy he had argued passionately against just a year earlier.
For the chancellor's critics, it was a sign he lacked the courage to be a true leader - that he was better off as a backroom operator, emerging into the spotlight once a year to deliver a densely-worded Budget speech.
But Brown, it was said, was conscious of not becoming Labour's Michael Heseltine - the assassin cast out by his own party after toppling a successful leader. (In Heseltine's case Margaret Thatcher)
He was also a party man to his fingertips. He did not want to provoke a potentially lethal war over the succession.
He had already become the longest serving chancellor in modern times. He could afford to wait a little bit longer.
Blair had, according to documents recently leaked to the Independent on Sunday, drawn up a secret plan to sack Brown after the 2005 general election and curb The Treasury's power.
He had already blocked Brown's membership of Labour's ruling National Executive and brought in his own man, former health secretary, Alan Milburn, to run the 2005 election campaign, in place of Brown.
But with Labour slipping in the polls, Blair was forced to bring Brown back to centre stage, making his record of low inflation and high employment, the centrepiece of the campaign.
Voters were treated to the familiar sight of Blair and Brown posing for pictures like old friends.
But although the old team had succeeded in winning an historic third term, the truce did not last long.
It culminated in September 2006 with Brown once again at the centre of an alleged plot to topple his old friend, as a string of junior ministers resigned over the prime minister's refusal to name a departure date.
Mr Brown denied any involvement but senior Blairites began openly questioning his suitability for the top job.
But a scramble to find a Blairite challenger to take on Brown - after Blair announced he was standing down - came to nothing as one-by-one they realised that being hammered in a leadership contest might not be a canny career move.
And by the time leadership nominations closed, Brown's total dominance of the Labour landscape was clear for all to see.
His task - as he launched his leadership "campaign" in central London - was not to prove he had the courage or determination to lead the party but the "humility".
Apparently stung by criticism of his "Stalinist" management style he pledged to "listen and learn" and to lead a government of "all the talents".
There will be more than a few Blairites - as well as Conservatives and Liberal Democrats - watching to see whether he lives up to those goals in Number 10.