The lack of weapons of mass destruction is evidence of historic failure

Every now and then, something happens that lights up the big picture. The tableau of history is usually shrouded in gloom, with only a few square inches at a time illuminated by the fizzing sparklers of daily journalism.

It has been apparent for some time that there are no weapons of mass destruction in Iraq, but the presentation of the interim report of the Iraq Survey Group - comprising no fewer than 1,200 inspectors - that was charged with finding them is a signal moment. It is only now, with David Kay of the CIA reporting to the intelligence committees, that we can see how extraordinary it was that this country - and to a lesser extent the United States - went to war to pre-empt a threat that turns out to have been false.

Quite how false becomes crystal clear from even the most cursory reading of the ISG's statement - which is presumably why the Prime Minister, fresh from his party conference triumph, took such pains to stress that we should read it very carefully, without rushing to judgement, and why the Foreign Secretary issued such a cautious statement, suggesting his own - and the Government's - authorised reading. As Mr Straw put it: "Kay's report confirms how dangerous and deceitful the regime was and how the military action was indeed both justified and essential to remove the dangers."

The key word here is "deceitful". For despite the best efforts of so many experts, who had free rein to probe wherever and whatever they chose after the fall of Saddam Hussein, the ISG's central message is that they have actually found no weapons of mass destruction and precious little of anything else. The only thing they found in vast quantities was conventional ammunition - largely unused, despite the US and British invasion.

In the absence of real weapons, Saddam's "deceit" is now the most heinous crime that can be laid against him. So deceitful was he, we are invited to conclude, that he tricked the best and brightest of the West's intelligence agencies and the politicians who relied on their assessments.

The statement delivered by David Kay yesterday is a litany of reasons why Iraq's weapons of mass destruction have not been found, why they may never be found, and why even supporting evidence for their existence has been hard to come by. Sites were looted after the US and British took power. The old regime selectively destroyed documents. The inspectors may now have the run of the country, but they are subject to attack by "insurgents".

The best that the ISG can come up with is a plethora of secondary documents and mostly inexact testimony from detainees, some evidence of "dual-use" imports, and repeated expressions of certainty that Saddam remained "committed" to obtaining, one day, the lethal weapons that our political leaders so confidently warned us he had. The ISG says that Iraq approached North Korea for longer-range missiles than it was allowed under UN resolutions, but offers no evidence that it took delivery of any.

For the rest, the statement's most outstanding feature is the dominance of conditional verb forms that suggest what Saddam might have been able to do, if ... Of actual biological, chemical and nuclear weapons, they have found not a trace.

Among its conclusions is a plea for the search to be continued. But not, we note, exclusively or mainly, in the expectation of finding any WMD, but rather to establish how much the pre-war intelligence diverged from the reality and how "the quality of future intelligence ... can be improved."

In this country, the attention paid posthumously to the government scientist David Kelly has had the effect of obscuring the single most shameful truth to have emerged from post-war Iraq. That truth is the failure of intelligence on a most remarkable scale and the failure of our political leaders, starting with Mr Blair, to exercise the judgement that was needed before they took us to war.