We have to remember that this tragedy began with something utterly unworthy of such an outcome. It was an extremely trivial point. It wasn't about life and death in war. It didn't deal in official secrets. It wasn't a case of espionage, betraying the security of the country. The point at issue was a story quite marginal to these things that might have mattered. It was: could Saddam Hussein have launched weapons of mass destruction in 45 minutes? The point that was stirred into turmoil, and then driven towards tragedy, was even narrower: whether Saddam could do this or not, who was the source of a BBC story saying some knowledgeable insiders did not believe it?
This is trifling stuff. In a normal political world, where top people had not taken leave of their senses, it would not produce a crisis. It certainly would not push anyone over the brink to suicide, if that's what happened to David Kelly. So you have to look further and see what made a triviality achieve all that.
The answer is regrettably simple. The 45-minute detail was hyped by Tony Blair into the essence of the foulest charge against his sainted integrity, and therefore had to be squashed by every means. The smell that's left behind is even more odious: that of a state - executive and parliament combined - willing to abandon all sense of proportion to score political points against its critics.
How a small detail, a sideshow, billowed into suicidal crisis is the government's work from start to finish. It alone put 45 minutes into the public realm, last September. Blair projected it further, in his introduction to the dossier. This was meant to shock, and it did so. Some of us thought and wrote that it sounded incredible. But there it was, doing the work it was designed to do: scare part of the country into supporting a future assault on Saddam Hussein.
Stage two of this infamous and potent - if virtual - 45 minutes came later. As war got closer and another dossier appeared, rumblings emerged from the intelligence world. There were reports, not least in the Guardian, indicating dissatisfaction among the friends at Vauxhall Cross, where MI6 is located. They didn't like the way politicians were turning the sceptical speculations of intelligence into firm public assertions, designed to play the same role as the 45 minutes: scare us witless into war.
But only when the main war was over did the notorious 45 explode to the top of the agenda. Again this was the government's doing. Andrew Gilligan, on the Today programme, reported, as an item of anxiety in the intelligence world, that one knowledgeable insider thought the September dossier had overhyped the 45. Because the 45 had been so graphic - the crown jewel in the glittering propaganda for war - maybe its tarnishing caused special pain.
Whatever, this was the moment at which Blair and Alastair Campbell decided to begin an exercise in hyperbole that soon swept every available particle of state power into the defence of their integrity. This involved them in several degradations. Here are some.
One, refuting charges that were never made: viz that Campbell inserted the 45 into the dossier knowing it to be false, whereas the real issue was one of presentational nuance, not overt falsity.
Two, using this minor issue to blur the far greater question overhanging the government at the very time the Gilligan story came out: viz did Blair tell the truth about why we went to war, and would WMD ever be found?
Three, insisting that the source of the story was what mattered, and squeezing every air pipe to try and get the BBC to disclose it - as if this mattered more than the manifest postwar fact that the 45 was always a myth, and the WMD probably no longer exist, for all of which, the prime minister now tells a confessional Congress, "history will forgive us".
A source, a source, my kingdom for a source, said Blair and his people. Once the source appeared, and as long as he was sufficiently unimportant, the credence of the critics of 45 would be destroyed. Enter David Kelly, an obscure though not unimportant consultant to both the Foreign Office and the MoD, who volunteered to his bosses that he had talked to Gilligan and maybe helped him on the story, without being his prime source. The honourable act of a man who had no idea he would shortly be thrust into the maelstrom that uniquely surrounds a prime minister who has decided that his integrity, if not his political life, is under threat.
There are secondary players in this sordid game. The BBC's and Gilligan's performance on the question of the source has been shifty. No doubt they had to be careful. Confidentiality is a sacred and essential rule. But when Kelly first appeared, they said the real source was in a different department, implying an intelligence official rather than a defence consultant.
Later they refused even to confirm or deny anything. This left the impression with some people that Kelly might indeed have been the source. Kelly himself, a man unaccustomed to the limelight, may have had the same sense that he was being fingered. If so, the BBC did its bit to add to the hideous pressure a delicate man was already feeling as the source Campbell/Blair needed and were imposing maximum pressure to unearth.
The recent behaviour of the foreign affairs committee of the Commons has been more ignominious. Its first report on the origins of the Iraq war was measured enough. It did not deliver all the exonerations for which Downing Street was looking. But then its chairman and Labour members seem to have got caught up in the frenzy of No 10, suddenly calling Gilligan for a second interrogation and coming out from behind closed doors to smear his reputation. Coupled with their gratuitous bullying of David Kelly to name himself as the culprit, these second-division politicians showed little respect for natural justice. Most of the Labour ones sounded like agents of No 10. They now seek a statutory ban on journalists having the nerve to conceal their sources from so august a body as a Commons select committee.
But the most eloquent message concerns the Blair government. It must be right at all times. Above all, the integrity of the leader can never be challenged. He never did hype up intelligence. He didn't take Britain to war on any other than the stated terms. Any suggestion of half-truth, or disguised intention, or concealed Bushite promises is the most disgraceful imaginable charge that deserves a state response that knows no limit.
That's how a sideshow came to take over national life. Now it seems to have taken a wretched, guiltless man's life with it. Such is the dynamic that can be unleashed by a leader who believes his own reputation to be the core value his country must defend.
· "Supping with the Devils", a collection of Hugo Young's writing, is published by Guardian books
© Guardian Newspapers Limited 2003