Blair's poised performance cannot mask the fatal flaws of Iraq mission

His explanation of why he took this country to war without the clincher evidence of Saddam's possession of weapons of mass destruction was more nuanced than previously offered in media interviews. And it lacked for nothing in conviction and self-assurance. The decision to go to war was not one taken on the balance of legal opinion, but on what Mr Blair judged to be the balance of risk at the time. Thus it was always in his eyes less about law than about the threat that an Iraq led by Saddam Hussein would continue to pose throughout the Middle East and beyond. Not only did Mr Blair stand by his decisions, but he went further in suggesting firm action would be needed on Iran.

With no WMDs discovered, he went out of his way to point to Saddam's lack of co-operation in coming clean about his weapons – or lack of them – which meant that Saddam was in "material breach", time and again, of his obligations to the UN. Mr Blair's performance was a reminder of his ability to make others overcome their doubts and persuade them, albeit reluctantly, to his side. This was the same Tony Blair who persuaded the Commons in 2003 of the rightness of his case, and who won a majority for that position.

Mr Blair's main argument was that decisions at the time were not based on absolutes, but on "the calculus of risk". In the more uncertain world after 9/11 it was simply too risky not take action against a dictator who had used chemical weapons on his own people.

He said that while the then foreign secretary Jack Straw had told the inquiry that legally and politically, the UK had wanted to take action to disarm Saddam rather than remove him, it was wrong to create a "binary division" between disarmament and regime change. Nor was the US assessment of Saddam's removal that of George Bush alone but also that of the president's predecessor Bill Clinton, who in 1998 believed regime change in Iraq was necessary because he could not trust Saddam to disarm. That the post-war death toll proved as high as it did owed much to Iran, which would explain Mr Blair's almost belligerent tone in speaking of that country.

But such explanations were never going to satisfy critics who view the legality of the war as the paramount issue and who could not stomach his perceived subservience to Mr Bush. But there are other issues which must colour judgment over his handling of Iraq. One was the marked lack of Cabinet consultation and discussion, leading to the sense of a one-man mission rather than a prime ministership. The second was the lamentable handling of post-war Iraq, and in particular the effective defeat of the British mission in Basra. This was a leadership found wanting, both in collegiate government and in the deployment of British troops. No "assured" performance can whitewash these.