When will British troops leave Afghanistan?

A CH-47 Chinook helicopter takes off after dropping soldiers in Bagh village of Khakeran Valley, Zabul province, Afghanistan Image copyright AP
Image caption Troops have been in Afghanistan since 2001

The prime minister told MPs today he enjoyed a "robust" relationship with the heads of the armed forces and enjoyed arguing with them.

He also dropped in to his chat with the Commons Liaison Committee that more than 400 British troops would be coming out of Afghanistan in the coming year. Could there possibly be a connection?

Today's comments follow reports of concern in the military about the Prime Minister's demands for an early withdrawal from Afghanistan and come ahead of a speech expected to be delivered by President Obama next month spelling out America's plans now that the surge is over.

It's clear that the Prime Minister wants to show that progress is being made towards the eventual goal of having no British combat troops in the country by 2015.

Meantime defence sources insist that the troops coming home have come to the end of their duties and would be returning whether or not Britain accelerates its withdrawal - since they include some, like those working out of Kandahar airbase, who are no longer needed.

The facts are clear - Britain's enduring force level will, for the moment, remain at 9,500 but there will 400 fewer British troops in Afghanistan by next February than there are now.

Behind the scenes I smell a debate going on about how quickly others should follow.