I was wrong about Saddam Hussein’s hidden Weapons of Mass Destruction. They never existed. We all talked ourselves into believing that there was something massive beneath the dry and dusty surface but when we got there the cupboard was empty. I am not going to make the same mistake about Gordon Brown.

It has become fashionable among some of my colleagues to murmur wisely that one must never underestimate the Chancellor. Andrew Rawnsley in The Observer often makes that point. “Never underestimate the Chancellor,” says Matthew d’Ancona in The Sunday Telegraph. In The Daily Telegraph, George Trefgarne advises that “the golden rule is: Do not underestimate Gordon Brown.” “Do not,” opines the Financial Times, “underestimate the Chancellor.” And the leading article in this newspaper yesterday offers the identical advice. Good heavens – who are this army of our fellow citizens prowling around and determinedly underestimating Mr Brown? Where can I find them? I want to join up. In my view it is urgently important not to overestimate Mr Brown.

I don’t believe in the Chancellor’s hidden intellectual superguns, his great schemes and plans under wraps, or his lurking genius. The much trumpeted deep thoughts, secret plans and massive subterranean firepower that it has become commonplace to claim for this man is all hot air. Who is privy to these thoughts? Who knows what these policies are? Where is the concrete evidence of this fathomless intellect?

On Monday, on Channel 4’s Dispatches programme, the political commentator Peter Oborne assembled a serious case against Mr Brown and his supporters’ claims that the Chancellor’s record recommends him. The real record, the programme argued, suggests otherwise: that he suffers from a crippling inability to get along with people, to listen, to learn or to bend.

It is some time since I have watched a more sure-footed or revealing political documentary. A wide range of voices, many of them hugely authoritative, some hostile and others sympathetic, and going back over decades, left viewers with the clear impression that there could be a big problem about this man’s personality. And because I mean to conclude that Oborne’s documentary, lethal though it was, missed its target, I must at once acknowledge that the assault was brilliant: the best-researched case I have seen for the proposition that the Chancellor lacks the personality to be Prime Minister.

He probably does. I do not disregard what Oborne came close to establishing. For those who did not see the programme (a comprehensive series of interviews with people who knew or had worked closely with the Chancellor) its conclusions can be summarised in a 13-point presentation. Brown is psychologically unfit for the office he craves, suggests Oborne, because: 1. He has persistent difficulty in handling human relationships with anyone who questions his authority or criticises his plans; 2. He snubs, cuts, bullies or ignores people he works with; he displays shocking ingratitude and bad manners; 3. He confines all serious deliberation to a tiny inner circle; 4. He will not let even senior staff know his mind; 5. He excludes talented equals from his circle and promotes talent only in juniors; 6. He punishes the bearers of bad news and favours those who tell him what he wants to hear; 7. He’s a control freak; 8. He transmits but seems unwilling to receive; he will not engage; 9. He seems unable to negotiate, he just keeps restating his position; 10. He is vengeful, given to ancient feuds; 11. He divides the world into a tight entourage that he can utterly trust and relax with, and an outer darkness of sworn enemies and uncertain friends, among whom he treads with suspicion, treating them gracelessly; 12. He hogs credit for himself and hates others to claim it; 13. He leaves other to take the flak and ducks when trouble looms.

All this rings true. Few of these traits, however, are confined to Gordon Brown alone. It is surprising how often top politicians seem to lack the personalities that would make them better at their jobs. But it remains true that so far Mr Brown has displayed a worryingly closed and leaden personality, lacking eloquence or inspiration, or any of those beguiling, charming or, at least, persuasive qualities that successful leaders often have.

I do not pretend that this may not be a problem. It’s just that, throughout history, lots of leaders could be judged temperamentally ill-suited to leadership – Margaret Thatcher was no great persuader; Churchill must have been hell to live or work with; Stalin lacked charm – but this did not stop them getting their way. There’s a reason for this. They had something big to do and the guts and imagination to see it and do it.

Mr Brown will not join their ranks. Three things will prevent his doing so. One is no fault of the Chancellor: he comes to office when there is no big, obvious thing that any prime minister is called on to do. Destiny has not supplied him with a simple challenge.

What will further disable him are two key personal faults – but not the faults Mr Oborne and others have identified. The first is that he lacks imagination. The second is that he lacks courage.

I am entirely ready to concede that Mr Brown is not stupid. I’m sure he’s good at sums and easy to brief. I accept what everyone says – that he’s well read. For all I know he has taken notes of everything he has read. I notice his mental agility at ducking questions and twisting arguments. And he obfuscates with something little short of brilliance: he can spar and bluster for hours without saying anything. But intelligence, real intelligence, involves lateral thinking, creative thinking. It involves thinking outside boxes, questioning basic assumptions.

For this you need two things: imagination and confidence. To sense Mr Brown’s deficiency in both departments, try subjecting a Brown interview – any interview – to close textual analysis. He gave what was reckoned a good interview to Andrew Marr last Sunday, and I have the transcript. From it emerges a mind forever scuttling fearfully back into a small range of comfort zones, where his answers are prepared and rehearsed. He has come into the studio reciting to himself “brownfield sites”, “cycle lanes”, “combined heat and power” and “public transport” and in the interview just keeps repeating them, as though terrified of being diverted into new territory.

My hunch is strong that in some strange way Mr Brown is afraid. Afraid of sudden choices, or surprises, or new situations. Note that weirdly contorted verbal formula he keeps using: “Education is my passion but health is my priority” – as though he dare not choose. Imagine a boy saying to his fiancée: “You are my passion, darling, but Mother is my priority” – or indeed: “You are my priority, but Mother is my passion.” Neither would wow the girl.

Consistent with this impression of a chronic failure of courage note, too, Mr Brown’s seemingly pathological horror of being anywhere where the flak is flying. It must have been obvious to his advisers that it would be sensible at least to show his face after the last local, Welsh and Scottish elections; one can only conclude that they could not make him – or, more disturbingly, he could not make himself – do it. It’s a sort of paralysis, isn’t it? When a confident striding into an argument or a situation is called for, his mental muscles seem to lock.

There’s an irony here. We all accuse Tony Blair of being the creation of spin, but the truth is that I don’t think he’s very different from the impression we have of him. I think Mr Brown is very different. His silence does not betoken strength; his immobility does not betoken carefully guarded plans. His curtness does not betoken honesty. His unyieldingness does not betoken valour. Mr Brown is the most spun politician of our era.

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