Fox flies the flag in Washington

The departure of General McChrystal from the top military job in Afghanistan will undoubtedly strengthen the arguments of those in Whitehall who have concluded that Britain is fighting alongside the US in an unwinnable war.

It will also likely stir further doubts in David Cameron’s mind about the conflict. The prime minister is said to believe that British troops should not stay a moment longer than is necessary to avoid a open rupture with the US; that means that as soon as the Americans start coming out – and Mr Cameron hopes that will be in mid-2011 – so too will be the British.

Few if any of the diplomats advising him believe that the present strategy is sustainable. “We are there because the Americans are there” is how one puts it. The mantra that defeat of the Taliban is a vital national interest is all but threadbare.

There is at least one minister in the coalition government, however, who seems determined to dismiss all talk of defeatism. Next week Liam Fox travels to Washington on his first trip to the US capital as defence secretary. The title of Fox’s planned major speech?

“Afghanistan: Standing shoulder to shoulder with the United States”