A bitter betrayal of Britain's trust

The murder of three British soldiers in Helmand by an Afghan soldier they came to train highlights one of the biggest problems in British and US plans for an exit strategy from Afghanistan.

One of the main aims is to build up a sufficiently strong Afghan national army and police force to bring stability and keep a moderate, if not pro-Western, government in power in Kabul.

It is hoped to have a viable army of about 275,000 and police force of just over 200,000 by 2014, by which time David Cameron wants British forces to cease combat operations, and most British forces to be out of Afghanistan altogether.

The need to scale down drastically the Afghan mission after next year is at the heart of the huge restructuring of Britain's forces, and defence and security profile altogether.

But how credible is the creation of a new army as the hospital pass for getting out of Afghanistan? Not as much as we may have liked to believe, it seems. This is the second incident of a crazed Afghan soldier turning his gun on his British trainers. On November 3 an Afghan soldier went berserk at Patrol Base "Blue 25" and killed five British soldiers in 30 seconds, among them the RSM of the Grenadier Guards WO1 "Daz" Chant, 40.

The new US commander in Kabul, General David Petraeus, is proposing to counter the misgivings about the new army and police by proposing the creation of local village militias loyal to the government - a key part of his strategy to turn the Sunnis against al Qaeda when he was in Iraq. But this is likely to create a new generation of Afghan warlords, living off the land and the people and reaping the huge rewards of the heroin trade.

The awful warning of the killing in Nahr-e-Saraj is that the Afghan strategy cannot be handled on the basis of Dickens's Micawber's that "something will turn up". Better heed the warning of Tancredi to his uncle Don Fabrizio in The Leopard: "Uncle, for things to remain the same, all things must change utterly."