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The UN path on to which the US was gently eased in 2002 by the UK and Americans such as Colin Powell was certainly preferable to unilateral US armed action against Iraq. However, for the UK to join the approach entailed a gamble: if inspectors were admitted, weapons found and destroyed, success could be declared. In the scenario that both the US and UK seemed to think more likely – that Iraq would, as it had done in the 1990s, resist or obstruct inspections – the security council might be persuaded to authorise armed action, which would bring both disarmament and regime change.

But if Iraq accepted inspections and made no obstruction and yet no WMD were found, how could the security council be persuaded to authorise armed action? And if it did not, where would the UK...