Davis obviously felt that given the row between Campbell and his employer, a diplomatic absence would be appropriate, even though everyone at Brown's bash would probably support the BBC.
Campbell wouldn't give a stuff what anyone thought about his actions in protecting Tony Blair, the fact is he has been spectacularly successful.
Margaret Thatcher's former press secretary Bernard Ingham was way off the mark when he claimed that Campbell had 'lost the plot'. The opposite is the case. Campbell has brilliantly plotted to divert all attention from the Prime Minister's decision to go to war on the basis of non-existent weapons of mass destruction and 'dodgy dossiers'.
Before the Prime Minister's spin doctor decided to attend the Foreign Affairs Select Committee, all the pressure was on Blair, not just for refusing to attend, but also for preventing the security chiefs from doing so, too. MPs were ready to rip the Government apart, especially for the dossier produced by Campbell that was plagiarised from a student thesis and used to support the war. His department even changed it to support the case for war, turning 'opposition groups' into 'terrorist organisations'.
You would have thought there could not be a more unreliable witness than Campbell. Indeed, you may even have thought he would have been sacked by now. But you underestimate Campbell at your peril. He knows the media loves nothing better than a story about itself and is particularly obsessed with spin doctors. Just appearing before the Committee was a big story in itself, but Campbell wanted headlines to deflect attention away from his boss. A weapon of mass distraction.
So he launched his exocet at the BBC. I went on TV immediately following his performance and said there was no way the media would fall for this obvious attempt to change the story - but how wrong I was. The BBC didn't help matters by responding to Campbell. They should, of course, have just said: 'This is a distraction - we stand by our story'.
Campbell couldn't believe his luck at the BBC response - although in fairness to it as a public service broadcaster, the BBC felt obliged to defend itself. Its own defence dossier was blown out of the water by Campbell's sensational appearance on Channel 4 News, and the story ran for yet another day. So confident had Campbell become by Sunday that he cheekily made a statement calling a truce until the Foreign Affairs Committee reports next week. The result of its findings is now not about Blair taking the country to war on a lie, but about Campbell's innocence and the BBC's guilt. There will, of course, only be one verdict from the Committee members - the Labour ones at least - and Campbell knows it.
In the short term Campbell may have got his boss off the hook, but his very presence at the heart of government is still a big problem for Blair.
The fact is, no one really trusts a word he says, and for the Government trust is something they desperately need to regain. The Tories have not climbed back up the opinion polls because of anything they have done, but because of what Labour has failed to do. If I were Blair I would wait a few months until the BBC row has gone away, and then quietly tell my spin doctor to go and spend some more time with his family.