This has been a gnawing question for quite some time. I have personally pondered that perhaps the Bush administration had promised him the capitalist equivalent of 70 virgins in the afterlife if he went along. This post from Juan Cole however, may, and I say may, explain the reason.
Essentially, Professor Cole suggests (with assistance from Obsidian Wings) that Tony Blair was terrified that the Bush administration was only interested in Iraq and was planning on totally ignoring al-Qaeda and the terrorist camps in Afghanistan. Blair therefore made a bargain of almost Faustian proportions; to wit, if you will attack the terrorist camps in Afghanistan with our help we will stand with you and attack Iraq. I have no idea how true this might be, but it has that "ring of truth" to it for me. Incidentally, you can expect the Guardian to have a ball with this. I do think that Blair will deny it, although I must admit I think it might be smarter for him politically to come clean with it, although that would of course leave Bush twisting in the wind in a huge way.
Posted by Alan at 22.03.04 21:44Blair claims that conflict with Iraq is about the possession of weapons of mass destruction. But that is his allegation and it's a partial reason. The unstated reasons are that oil is part of the equation, along with the wider strategic interests of the US in the middle east. Blair claims he does not go to war lightly. Yet Blair has supported bombing in the former Yugoslavia, Afghanistan, Iraq and elsewhere. The UK is a major world arms trading nation. When not at war Blair and his 'new world order' friends in the US maintain a state of half war. Thousands upon thousands of innocent civilian lives have been lost in countries which Blair has helped bomb since 1997.
Posted by: Chilton at 20.10.04 08:46