He squandered it on September 24 last year as he spoke to a mesmerised House of Commons, presenting his dossier of intelligence information on Saddam's weapons. It was a bravura performance, spellbinding in its quiet solemnity, reasoning the arguments one by one, blending conviction with eerie threats. Forty-five minutes! Good God! You could see the MPs' hairs standing up on end, calculating how far this holocaust might reach. That precise timing resonated with a generation that grew up discussing what to do in the four-minute nuclear warning - run a mile, boil an egg, have sex... In that speech he over-egged it and he must have known it. Whether Downing Street demanded the fateful "45 minutes" or not, he knew - and it is there in cold print - that the chilling words ran far beyond what anyone knew for sure.
Reading his introduction to the dossier, it is careful in its caveats, filled with "probably", "appears" and "almost certainly". "Intelligence is not always right" and "gathering intelligence inside Iraq is not easy" pepper the text. But between these come the deadly shockers - one-and-a-half tonnes of VX nerve agent, 26,000 litres of anthrax spores, 30,000 special munitions of delivery - and then that killer 45 minutes. "Our purpose is disarmament," he said. "The whole purpose" was "a proper process of disarmament".
But now Donald Rumsfeld shrugs that off as an irrelevance. Well, Saddam may have destroyed them all before the war began. We can only hope he is right since Robin Cook raises the alarm that they may yet emerge lethally: "The prospect of any chemical shells or biological toxins being left unguarded in such an unstable region is a nightmare." What if Qusay took them away with him in his trailers full of cash? What if the war to stop WMD falling into the hands of terrorists turns into the means by which terrorists finally get their hands on them? "A savage irony," says Cook.
Apart from that danger, it makes no difference now to the justification for the war if they are never found or accounted for. After all, Hans Blix always said they were there and we who opposed the war never doubted it. The only important question was how dangerous they were and whether Saddam would or could use them. Saddam's non-use of the weapons even in the death throes of his regime was conclusive proof that he had none he could use. Weapons inspections had done their work, forcing him to render them unusable. So far, the US says, Iraqi scientists have revealed nothing useful. Yesterday Blair promised some WMD would be found - but it changes little: they were not used. Why not? Reading Saddam's deranged mind was beyond the intelligence services, but pride and the habit of absolute power perhaps made him unable to bend to the UN, even if he had nothing much to hide. Tony Blair put his credibility into the hands of Saddam's caprice.
But the question will never go away now - did the prime minister lie that day? There can be no avoiding an inquiry with the power to summon the intelligence witnesses who provided the information. The Guardian today suggests a committee of privy counsellors would do better than MPs. If the intelligence services have been badly traduced and their tentative information was spiced up by Downing Street, then they deserve to be exonerated. But if, as Downing Street now says, not a word of the dossier was changed and the intelligence services themselves over-egged it, then Blair needs to be proved innocent of lying - however wrong his judgment about the war.
Until it is discovered exactly what Saddam had and what he did with it, it will be hard to ascertain how good the intelligence information was. It may never be clear to what extent intelligence services lean towards arming their paymasters helpfully in moments of crisis. They are not stupid. Adam Ingram, the armed forces minister, was adamant in his denials yesterday of Downing Street pressure or concoctions. For now, there are too many unknowables.
As for Tony Blair's veracity, with him there is a wavy line between deception and self-deception. He is so easily carried away by the persuasiveness of his own words and the force of his own arguments that you can hear him mesmerise himself: the truth with him is bound up with extraordinary optimism. There is an almost childish blurring between the wish and the fact: if he says something strongly enough, his words can magic it into truth.
There does remain the shocking affair of the forged documents used to persuade the US Democrats that Saddam had acquired a phenomenal 5,000 tonnes of uranium from a Niger mine. Seymour Hersh, the great American investigative reporter, writing in the New Yorker and Prospect magazine, follows the trail of badly forged documents right to the door of Britain's MI6. Even if MI6 did not create them, it circulated them and swung not only British opinion and perhaps the prime minister himself, but effectively silenced the Democratic party for the duration. This "hard evidence" that Saddam was going nuclear frightened the life out of all who saw it. Who did it? Or who in our intelligence services saw such a botched forgery and pretended to believe it? (The Niger minister supposed to have signed it had been out of office since 1989.) Only a high-level inquiry can find out who did this.
Striding through Basra in his bright white shirt yesterday, kissing babies and praising troops, this was as near as dammit a prime ministerial triumph. But all around him lies the wreckage - wild lawlessness, monstrous looting and killing, our own cluster bombs, no police, no water, no electricity and the dangerous boiling fury of people who find the white knights who came to save them look more like the horsemen of the Apocalypse right now. True, it's early days and the test is how Iraq fares two years from now. This is not the time for I-told-you-so gloating by those of us who opposed the war: it is better to live in hope that, out of the ruins, a better Iraq might still arise. But the utterly inept, penny-pinching US nation-building effort and their amnesia about Afghanistan makes that hope slender.
Shock and awe show no signs of striking sense into Muslim fanaticism. Quite the contrary - the world feels more dangerous. "You made our country hold its head up high," Tony Blair told the troops yesterday. If only that were so. Nul point, Europe replied last weekend, and the Olympic committee may be similarly inclined. The day Tony Blair has to fight the next unpopular cause - Europe - the people may be less willingly persuaded by his rhetoric: that will be a critical political loss.