So, what did we achieve? After four years and 174 dead, Britain's lead role in Basra is over

At that point, more than three months ago, the Iraqi army and police effectively took over security in the area which contains more than 70 per cent of the country's proven oil reserves and supplies 90 per cent of government revenue. Nor, after the ceremony, will hundreds of British soldiers be relieved of their duties in time to fly home for Christmas.

Prime Minister Gordon Brown has already outlined the timetable: the 4,500 troops remaining at the contingency operating base, known as the COB, at Basra airport will gradually be reduced by 2,000 over the first three months of 2008. Those left will continue training Iraqi forces and maintaining an "overwatch" role, ready to intervene in an emergency if asked to by the Iraqis.

Despite their retreat from the streets of Basra, British forces are not completely out of danger. Last week Guardsman Stephen Ferguson of the 1st Battalion, the Scots Guards, was killed when his Warrior armoured vehicle slid into a canal. He was the 174th British soldier to die in Iraq since the invasion. And, though the British force has not suffered a death from "hostile activity" since September, rocket and mortar attacks on the COB continue. Many of the troops still sleep in tents, with blast walls made of breeze-blocks or sandbags surrounding each bed, so that, while a direct hit would be fatal, the rest of the tent's occupants might escape without serious injury.