Britain promised 8,000 frontline peace-keepers

The Government may insist it will not supply combat troops to the United Nations peace-keeping mission in Sierra Leone. But if the British force being amassed in the area does end up in that role, it would be exactly as Britain has long promised Kofi Annan.

Last June, in the afterglow of Kosovo, Britain and France signed separate memoranda placing forces on permanent stand-by for emergency UN peace-keeping operations. Britain's target contribution was a full brigade, up to 8,000 men, consisting of frontline troops for rapid deployment, backed by aircraft, communications and engineering units and full command and control.

The force would not be the nucleus of a UN standing army, Robin Cook said, and Britain would naturally retain a veto over the use of its troops in any given operation. But, as he said in June: "The problem for the UN is that every time there is a fire, they have to build a fire-engine. At least now it will have the components for the fire-engine."

The concept also dovetailed with Tony Blair's "doctrine of international community," enunciated during the Kosovo campaign, giving outside powers the right to intervene against "threats to international peace and security". It also tied in with Mr Annan's insistence that protecting human rights took precedence over national sovereignty.

In military terms the planwas a logical outgrowth of the 1998 Strategic Defence Review, refashioning Britain's armed forces for the post-Cold war era; giving them global reach, above all for peace-keeping missions. All the strands have now come together in the Sierra Leone crisis. And whatever ministers say, the size of the force Britain is assembling - 800 paratroopers on the ground already, backed by 550 marines and the support capability of a seven-ship task force led by the aircraft carrier HMS Illustrious - means it is one whose role could change very quickly.

The first priority is the evacuation of British, EU and Commonwealth citizens. But senior officials say the force, expected to reach Sierra Leone by the weekend, could extend its mission by two or three weeks, until better equipped UN peace-keepers from Jordan and India arrive, alongside perhaps a return of the Nigerians. But, British diplomats say, "the quality of the incoming troops will be vital". In the meantime, they acknowledge, the very presence of élite British soldiers is having a calming effect.

The longer British forces remain the greater becomes the familiar dilemma of "overstretch" - the widening gap between the government's international commitments, and its ability to find the men and money to fulfil them.

The Army is currently 5,000 under-strength but the expertise of Britain's military has never been in greater demand. British soldiers are on duty in some 80 countries, in missions ranging from tiny training projects to the combined 6,500 men stationed in Kosovo and Bosnia. New crises -- in the Gulf for example, or a full scale evacuation emergency in Zimbabwe - could stretch those resources even further.