But the hearing did give him the chance to underline an important point that was missed in the huge build-up - that he's not quite as all-powerful in his own right as his critics frequently make him out to be.
Implicit in both the awe, and the criticism, of Mr Campbell is the fanciful notion that it is his own power he is exercising rather than that of his boss.
Tony Blair, we are supposed to infer, would be quite happy, say, for Harriet Harman and Frank Field to thrash out their differences in public if only Mr Campbell didn't keep dashing off those peremptory missives telling them to can it. It is, as he made clear last night, nonsense. True, as one of Mr Blair's closest friends and confidants he has real influence; he will, for example be among the select few consulted on next month's reshuffle. But the authority he exercises in Whitehall is not his own but the Prime Minister's. Mr Blair may seem like a nice, laid- back kind of guy. But that's possible because Mr Campbell, with Mr Blair's full approval, is occasionally just the opposite.
Yesterday he was adamant that he had not briefed against anybody: "I can and I can also respond to what Bernard Ingham [Margaret Thatcher's former press secretary] said in his evidence [to the committee] when he stated as a fact that I had briefed against David Clark and Frank Dobson and two or three others.
"I have not briefed against any members of the Cabinet. Again, you can ask your journalists, you can call them in. I happen to think you can put across the Government case in a coherent and co-ordinated way without frankly briefing against anybody."
Neither, he said, had he been the source of stories in two Sunday newspapers in which - after rows about a biography of the Chancellor - it was suggested Gordon Brown had been described as "psychologically flawed" by a senior figure in government.
To understand the limits of Mr Campbell's alleged omnipotence, consider his famously old Labour views on education. He was personally aggrieved by Ms Harman's decision to send a son to grammar school. He would probably ideally like grammar schools and public schools to be abolished. But if he said so he would be sacked within minutes. If John Prescott said so, it would cause a huge public debate on the future of education policy; but he would be highly unlikely to lose his job.
It's true that before the local elections Sir Richard Wilson, the Cabinet Secretary, warned Mr Campbell, as permanent secretaries throughout Whitehall warned their departmental press officers, not to use their jobs to score party political points. It's also true that Mr Blair was being more than a little cavalier when, defending him in the Commons, he commented that one reason he was under attack was that "he does an effective job attacking the Conservative Party."
That was indeed one of his jobs in Opposition, but it's not what the taxpayers have been forking out his pounds 87,000 salary for since the election. And he appears to know that now. Last week, as he told the MPs last night, he consulted Sir Richard on whether he was within the rules to brief on Peter Temple-Morris's defection to Labour. Sir Richard said the case was borderline, and Mr Campbell left it to the party to handle.
What he does have is a lot of knowledge. He is Top Secret Positively Vetted - Whitehall-speak for being cleared to receive the most sensitive documents.
The first of several conversations he has with the Prime Minister every day sometimes takes place before he reaches the office at around 7.30am, having read the media brief faxed to his home in South Hampstead about an hour earlier. He never lunches. And because he has such a close relationship with Mr Blair, he has no urge, already working a 100-hour week, to attend at meetings he doesn't have to be at. But he goes to all the important ones he wants to. And he sees all the Cabinet Committee papers.
He doesn't do everything. One of Mr Blair's undoubted talents is to use horses for courses. Mr Campbell was the right choice to bring the Tottenham Hotspur boss, Alan Sugar, over to Labour before the election and to arrange the Japanese prime minister's famous "apology" in the Sun. He wouldn't be the right man to co-ordinate a government initiative on the performing arts. He did, when asked, as he surprisingly frequently is on such matters, give his opinion who would make a good political editor at the Daily Express.
He would probably admit that he could have handled the notorious Clinton letter on Ulster - which went to the Sun when the Mirror thought it had it exclusively - better than he did. And he could have been franker from the beginning than he was about Mr Blair's famous phone call from Romano Prodi, the Italian Prime Minister.
On that phone-call, Mr Campbell said yesterday he had never briefed on the contents. He rejected suggestions he had somehow changed his story and, in typical style accused some newspapers of "pursuing their own commercial interests" over the story, which focused on the activities of Rupert Murdoch, head of News International.
But journalists aren't - or shouldn't be - prairie flowers. There are certainly times when they should argue back more than they do. But the best batsmen know how to play spin.
What they get with Mr Campbell is someone with high intelligence and scarcely-rivalled knowledge - greater even than Sir Bernard Ingham had of Baroness Thatcher - of the Prime Minister's mind and, for the most part, a willingness to share it. And they know exactly where he's coming from.
On message and off message ...
Alastair likes... Bagpipes. Alastair Campbell was taught to play them by his father, a Scottish vet, and at one time he earned extra cash by busking. "The French are much nicer to buskers than the British," he once said, "and they like pipe music."
Bernard Ingham, Margaret Thatcher's press officer. "It would be absolutely pre- sumptuous of me to assume I'm going to do Bernard Ingham's job. But if I can do for Tony in opposition what Ber- nard did for Maggie in office, I would do pretty well," he said after he was appointed.
Burnley Football Club. When Campbell held a party at the Reform Club to celebrate his appointment as press secretary, the chairman and manager of Burnley FC were invited, as well as Neil Kinnock and James Callaghan. Fists (occasionally). Mr Campbell famously hit the political editor of the Guardian, Michael White, on the day Robert Maxwell died. At the time he worked for the Daily Mirror. "Mike kept repeating his joke: 'Now we know why he's called Captain Bob-bob-bo b-bob.' Eventually, I saw a blue mist and lashed out."
Alastair doesn't like... Alcohol. As a young reporter Mr Campbell drank heavily but gave up after a breakdown. He once said that on a not untypical day he consumed 15 pints of beer, half a bottle of Scotch and four bottles of wine with David Mellor over lunch.
Pornography. When Edwina Currie put the parliamentary portcullis on the front of her smutty novel, he said she should be had up for "bringing the game into disrepute".
"Arrogant and over-staffed." - On the BBC
"One of the most tedious, silly pieces of television ... I thought it was pathetic."
- On the BBC's 'Panorama' about spin-doctors
- Reportedly on Gordon Brown
"It's balls that the Prime Minister 'intervened' over some deal with Murdoch. That's C-R-A-P."
- On reports of Tony Blair's phone conversation with the Italian Prime Minister about Rupert Murdoch's bid for an Italian TV station
"There is one reason why the Tories attack the press spokesman - he does an effective job attacking the Conservative Party."
- Tony Blair on Alastair CampbellReuse content