If barely concealed driving ambition were enough to make a Prime Minister, the job would be in Mr Brown's pocket. But, as the biographer of the man from the manse with the "strong moral compass" explains here, it's far from a done deal despite the Chancellor being the best candidate for the position

Until the extraordinary outbreak of near-civil war in the Labour Party last week, the most frequently asked questions about Gordon Brown were: what sort of a Prime Minister will he make? And, is he really as dour as he looks on television? But after the open warfare between the Blair and Brown camps, a third question came to people's lips: is he still going to become Prime Minister?

This third question followed the printing of allegations that Mr Brown was either behind what rapidly became a failed coup to oust the Prime Minister, or at the very least behaved dishonourably by failing to intervene in public in support of Tony Blair. The most vociferous accusations came from former Secretary of State for Education and Home Secretary Charles Clarke who, only a week earlier, had warned against the dangers of the Labour Party being consumed by fratricidal strife.

Mr Clarke not only pointed the finger of suspicion at Mr Brown, he also raised questions about the Chancellor's character, and suitability to be Prime Minister. This was not the most obvious contribution to the avoidance of fratricidal strife. And, although Mr Brown made a most magnanimous gesture of forgiveness of Mr Clarke when he appeared on BBC television over the weekend, the damage had been done, and there was much speculation about the advent of a "stop Brown candidate".

It had soon became apparent to both the Brownites and the Blairites (as they have become known) that short-term scoring of points against each other was causing huge damage to the Government's reputation. Encouraged by the party's elder statesmen, they embarked on an exercise in "damage limitation" and a truce was declared. The outcome at the time of writing appeared to be that the Brownites had finally secured a public commitment from the Prime Minister to step down before the autumn of 2007, and the Blairites had, they hoped, ensured that the Chancellor would call off the dogs. Those Blairites who wished to spoil Mr Brown's chances of succeeding to the premiership were also able to derive some satisfaction from the Chancellor's public statement that there should be a proper election to choose Mr Blair's successor, and not a "coronation" (of Mr Brown).

The idea of a "coronation" had not looked right to the general public, let alone to the Blairites. And the entire squabble may yet prove to have done lasting damage to the Government, even if the truce holds. Which brings us back to those three questions.

Working backwards, we can begin with Mr Brown's chances of becoming Prime Minister. In this context it is important to emphasise that both Conservatives and Labour are good at springing surprises: well-qualified candidates such as Roy Jenkins and Denis Healey never secured the Labour leadership; John Major was not sidelined in favour of the most obvious choice for the succession to Mrs Thatcher. This said, Gordon Brown is widely acknowledged to be head and shoulders above all rivals, and his support in the Labour Party's electoral college (a mix of MPs, unions and constituency Labour Party members) is such that he must remain the firm favourite.

Is he as dour as he looks on television? No, he isn't. He can be moody, as Charles Clarke will be happy to testify. There is a saturnine aspect to his character - but Churchill's "black dog" was surely a much greater handicap. However, most people who meet Mr Brown in person for the first time find a charm and sense of humour they had not been led to expect. And in his interview with Andrew Marr on BBC television last Sunday there were signs that, at last, the Chancellor is beginning to appear less dour on camera - an important development in the television age.

So to Mr Brown as Prime Minister? (To which the "character question" has been added as a supplementary by Charles Clarke.) Here we have a very unusual situation. In a sense Mr Brown has been half a Prime Minister for 10 years. Under the terms of the now infamous "Granita Agreement" - named after the Islington restaurant where Mr Brown agreed after John Smith's death in 1994 not to stand against Mr Blair for the leadership - Mr Brown was granted an unusually wide brief. All chancellors, ex officio, tend to have an interest in other Whitehall departments, because they are responsible, on our behalf, for ensuring that taxpayers' money is well spent. But, thanks to the Granita Agreement, and his own forceful personality, Gordon Brown has exercised more control over the actual policy decisions of other departments (most notably in the social security area) than previous chancellors.

This arrangement, in addition to the doctrine of collective Cabinet responsibility, has inhibited Mr Brown when it comes to the number-one political issue of our time, Britain's position on the invasion of Iraq. On the big issues Tony Blair has been his own Foreign Secretary, just as Eden was 60 years ago at the time of Suez, with comparably disastrous results. The principal reason why Mr Blair is being forced to step down is that, as a result of Iraq, he has become an electoral liability. Labour MPs discovered this on the doorsteps during last year's general election campaign, and Mr Brown had to be brought back to the centre of the campaign, having been sidelined in favour of former Health Secretary Alan Milburn. (When critics of those who want Mr Blair to step down complain that this is unfair to a man responsible for three election victories, they might reflect that the 2005 election was almost certainly won in spite of Mr Blair.)

Rebel Labour MPs were then forcefully reminded of the strength of feeling about Mr Blair's foreign policy when they returned from their August holidays and met constituents who had been horrified by Mr Blair's connivance in President Bush's support for the bombing of Lebanon.

In a sense the Blair premiership has been a duumvirate of Mr Blair and Mr Brown, with one concentrating on foreign policy, one on the economy, and both supporting the allocation of extra resources to the public services, with plenty of scope for differing about the details (hence all these arcane arguments about "choice" and "diversity", and the more tangible differences about the degree to which the private sector should be involved in delivering public services).

Thus Mr Brown as premier would have a wealth of experience under his belt. The idea that the co-founder of New Labour would wish to return to the bad old days when Labour was so left-wing that it was unelectable is absurd; but it is a convenient myth for peddling by the many Conservatives who are fearful of this formidable politician.

Some observers complain, in that inelegant phrase, that Mr Brown is "a control freak". But so is Mr Blair. It is just that Mr Blair for a time had a better way of concealing this. Alas for the Prime Minister, his controlling instincts over foreign policy spun (I use the word advisedly) completely out of control. Politics is a rough old trade, and Mr Brown has trodden on many toes. But so has Mr Blair: behind that easy smile is the hard man who sacked his own patron, the Lord Chancellor Lord Irvine, who was trying to restrain him in his assault on civil liberties.

As Prime Minister, Mr Brown would be forced by the demands of the job to delegate and become less obsessed with detail. There are strong signs that late fatherhood has helped to make him a more relaxed person. He feels he has been misled, not to say double-crossed, many times since the "Granita Agreement". An impartial observer may be forgiven for saying "so what?" It is not very British to believe that accession to the premiership should be dependent on some private deal (and the Chancellor is a great one for Britishness these days). Nevertheless Mr Brown's sense of grievance has affected his relations with Mr Blair, and contributed to the in-fighting that the public finds so baffling, not to say contemptible.

The two of them started in 1983 as the best of friends and colleagues. The problem in recent years has been Mr Brown's suspicion that Mr Blair was procrastinating in order to spoil his chances of succession. In so far as Mr Blair's premiership is regarded as one of the most successful for any Labour leader (obviously, we are talking only of domestic policy, including Northern Ireland), much of that is down to Mr Brown. Mr Brown is the best man to succeed him. Most senior politicians and civil servants know that Mr Brown is the best person to succeed Mr Blair. He was not exaggerating when he said in the BBC interview that he had inherited a "strong moral compass" from his father, and that should be an invaluable guide if he succeeds to the premiership.

While there is no better candidate in the present Labour Party, would he be a good Prime Minister? Here we are in the realm of Macmillan's famous "events, dear boy, events". But it would certainly be fascinating to see what he made of it. I cannot think of any British politician in recent decades who so patently wanted the job so much.

William Keegan is a business columnist with The Observer, and the author of The Prudence of Mr Gordon Brown, published by John Wiley & Sons.

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