It was the first big name. The scene outside the Queen Elizabeth II Conference Centre in Westminster this morning reflected the anticipation. Photographers thronged the entrance, policemen lined the streets, television presenters perched like birds along a wall waiting to go on air. The queue for public access was the longest it had been since the Iraq inquiry had begun, said a dedicated inquiry-goer ahead of me in the queue. "Do you think he'll come clean?" one woman asked enthusiastically.

The moment Campbell stepped out of his car, he was mobbed by cameramen -- policemen had to fight them off to let him through. Once inside, I heard two inquiry staff members discussing his arrival. "It was savage," said one. "He [presumably Campbell] said it was worse than Hutton."

But Campbell, it quickly became clear, was not going to "come clean" despite prodding from the panel (mostly from Sir Roderic Lyne, who was by far the most needling and interrogative of the committee members). In fact, he was going to do what he does best: stay resolutely on-message.

Parts of the press are running the "letters" story -- that Tony Blair pledged Britain's support for the Iraq war in a series of notes (which Campbell saw) to George W Bush in the course of 2002, while publicly backing the diplomatic process. But in reality, for five hours straight, Campbell doggedly defended both the decision to go to war and the process leading up to invasion (he admitted government weakness only in the aftermath of the war).

As he put it: "I defend every single word of the dossier. I defend every single part of the process."

That's not to say he wasn't rattled, or that inconsistencies weren't thrown up by some of Lyne's more persistent lines of questioning. Campbell never thought it necessary, for example, to clarify the 45-minute claim as it was reported in a number of newspapers. (His excuse? That if he had spent all his time countering false stories in newspapers it would have absorbed him "24/7".) Nor did he see anything wrong with his chairing of the meetings that put together the case for war, despite, at the very beginning of the session, insisting that he was "not a policy person. I never was." He chaired, he said, because of the "support" he was giving John Scarlett on "presentational" aspects of the dossier.

Further questioning on the dossier only elicited Campbell's wrath, directed mostly at the media. He still seemed obsessed by Andrew Gilligan's report on the Today programme that claimed his dossier was "sexed up", constantly repeating his belief that the only reason why people questioned the dossier was the hyped-up media reporting. Clearly his contempt for journalism in this country hasn't abated, either (he complained of "conspiracy theories" published in the Guardian yesterday).

By contrast, Campbell's loyalty to Blair, in his defence of the previous prime minister's "conviction" about Iraq, was passionate. But he also turned to Blair to help him in his stickiest moments -- as Lyne challenged him over the dossier's claim that the intelligence was "beyond doubt", Campbell tellingly shifted the focus. It was the then prime minister's "belief", and fundamentally his final "judgement", that Iraq was a growing threat. He was loyal, unquestionably, but his evidence also set the stage for Blair's appearance before the inquiry later this month.

Campbell was a strange combination of vague and pugilistic. He veered from not being able to recall meetings or conversations (even some of the most important, such as the conference between Bush and Blair at Crawford) to bullishly recounting the exact dates of media reports and their contents. He quibbled about semantics or the "philosophical" question of how you define the UN.

But, over and above it all, he was adamant: he would defend the course of events that led to the invasion of Iraq until the "end of his days". Not only that, but Britain and her people should be "proud" of what we did. The shaking heads in the public audience didn't seem to agree.