History throws up uncomfortable symmetries. The foreign policy pursued by Tony Blair was originally forged in the aftermath of a failed adventure in the Middle East more than four decades ago. The principal actors in the drama were Britain and France on one side, the US on the other. The prime minister's policy is now being tested to destruction by another military foray in the region. This time the divide is between the US and Britain, and France.

Mr Blair's decision to go to war against Iraq conflated Gladstonian moralism with conventional strategic purpose. It was right to rid the world of Saddam Hussein; and, yes, he did believe the Iraqi leader had weapons of mass destruction. Above all, though, regime change in Baghdad would mark the limits of the west's tolerance of unconventional weapons proliferation.