By Paul Reynolds
World affairs correspondent, BBC News website
Mr Brown was chancellor at the time of the 2003 invasion
The British Prime Minister Gordon Brown based his defence of the Iraq war on the theme that the post Cold War world could not tolerate states or terrorists defying international obligations and rules.
In this he differed somewhat from Tony Blair, the prime minister at the time, who argued that it was 9/11 that had changed the perception of Iraq as a threat.
Subtly, Mr Brown distanced himself from the war-making process, saying basically that he was in charge of finance not strategy, though he accepted that it was a strategy he agreed with and financed to the fullest extent.
However, he did not lay any blame on Mr Blair and, like Mr Blair before him, Mr Brown did not express any reservations or doubts, beyond admitting that planning for the post war period was inadequate.
Like other British officials have done, he blamed the Americans for that, without explaining why British planning for its area of responsibility around Basra appears to have been no better.
Addressing the concerns of his domestic audience about the equipping of armed forces both in Iraq and Afghanistan, he defended himself by saying that no request were turned down for Iraq and that helicopters for Afghanistan had been fully funded.
He mentioned the "rising" budget of the Ministry of Defence numerous times.
Throughout he seemed as concerned to answer criticism of equipment procurement as he was to defend the war in Iraq.
The members of the inquiry struggled to make dents in his arguments for the war and he was able to make a series of statements which critics of the inquiry might feel should have been picked up.
Here are some of them.
In setting out his case, he stated that Iraq had not "honoured its international obligations", a reference to UN demands after the first Gulf War in 1991 that Iraq open itself to inspection and disarmament. This was true to an extent, but it was not pointed out to him that Iraq had in fact been largely disarmed after the first war, so had been brought into major compliance, albeit by pressure and sanctions.
Another example came when he said that under Security Council resolution 1441 of 8 November 2002, "the weapons had to be disclosed", referring to the weapons of mass destruction Iraq was believed to have. "This did not happen," he stated.
He was not challenged as to what weapons these were, since (apart from missiles which did exceed the limits imposed by the UN), Iraq did not possess any.
Mr Brown was left implying that Iraq did in fact have such weapons.
He did this more than once. At another point he said that Saddam Hussein "did not disclose, far less dismantle any of his weapons" after the November resolution, which had given Iraq in a final chance to comply.
Again, he was not asked "What weapons?"
A third example came when he constantly referred to the efforts to get a diplomatic solution at the UN in the final weeks. He blamed "countries" for blocking this (being pressed to name the French among them) and for thereby forcing the issue to go to war.
He was not questioned about the nature of those diplomatic efforts, much of which were designed to bring the whole Security Council behind a decision to go to war. The French and others did not block a solution with Iraq, they blocked a clear Security Council authorisation for a war with Iraq.
So Mr Brown was able to leave the impression that the unreliable French were responsible for blocking peace, just as the unimaginative Americans had been responsible for the post-war chaos.
Aware that the inquiry is tasked with drawing lessons from the war, he offered his own.
They included a concept of the "just peace" by which he meant, not a democracy, as he put it, "conjured up" at "the point of a gun" favoured by US neo-conservatives, but a system of building up support among the people.
This lesson, he said, was being applied in Afghanistan.
He called for a new UN agency to develop this concept. However, given the international divisions over Iraq, it appears unlikely that this will happen anytime soon.
The issue is whether the Iraq war provides an example of how a rogue state can be tackled or whether it has made concerted international action more difficult.