Gordon Brown’s announcement of the conditional dispatch of a further 500 British troops to Afghanistan represents a sop to the Atlantic alliance, rather than a change of heart in Downing Street. The prime minister and his advisers are deeply sceptical – as is President Barack Obama – about whether a reinforced combat effort will change much in an increasingly unpopular war.

But the American military has exerted huge pressure on the White House and US allies. “We face a crisis of confidence,” Stanley McChrystal, the US and Nato commander in Afghanistan, told an audience in London recently. “This effort will not remain winnable indefinitely.”