Ake, the reason you went into Iraq was because Iraq is sitting on one hell of a lot of oil, and Saddam Hussein had made the decision to sell that oil for Euros, not dollars, and the USA was willing to invade Iraq over that little matter, and Britain and the USA have a common policy in regards to working as partners to control as much of the world's oil as they possibly can, specially in the Middle East.

That is why you invaded Iraq.

As you say, pure expediency...but not political expediency. Politically, it was disastrous for both Blair and Bush. No, it was economic and financial expediency that lay behind their actions.

Ironically, though, their war has cost so much money that it appears to have defeated its own purpose, at least in a financial sense...although they do have the desired control of the Iraqi oil now.