A Royal Marine attached to the special forces has been killed - and four other British servicemen injured - in in a firefight in Iraq.
Corporal Ian Plank was a member of an Anglo-American force operating near Baghdad, outside the British-controlled zone in the south of the country, when he was shot dead.
The killing brought Britain's death toll in Iraq to 52, 19 of whom have died since the end of major operations on 1 May. The total number of American fatalities in military operations is 377, with 139 killed since the end of the war.
Cpl Plank, 31, from Poole, Dorset, was killed on 31 October but news of his death was not revealed by the Ministry of Defence until yesterday for "operational reasons".
The British zone, centred in Basra, has been relatively quiet, unlike US-controlled areas which have seen rising violence. Britain has refused requests from Washington to send troops to join American forces in Baghdad. But members of the SAS and SBS have been taking part in undercover operations with US units.
The Prime Minister was "deeply saddened" by the news, his official spokesman said. "We have always been aware the work our troops do in Iraq is dangerous and valuable, and the Prime Minister has always been very aware of the risks our soldiers run. At the same time as he believes their work is highly to be valued," he said.
Colonel Jerry Heal, director of the Royal Marines, described Cpl Plank as an "extremely popular and greatly admired marine", widely respected for his professional excellence, commitment and determination.
"He was particularly well known for his resilience and robustness under pressure, when his leadership, example and sense of humour were especially valued. He embodied all the personal and professional qualities associated with the Royal Marines and he enriched the lives of those who knew him.
"His positive outlook, bright disposition and zest for life will be remembered with deep pride and affection by all who knew him, and most of all by his family and members of the Royal Marines and others with whom he served."
Iain Duncan Smith, the outgoing Tory leader, said: "We deeply regret the death of Corporal Ian Plank. The work he and other soldiers have been doing in providing peace and genuine freedom for the Iraqi people has not been acknowledged enough. Our thoughts and prayers go out to his family. Let us hope and pray that his actions were not in vain."
Paul Keetch, the Liberal Democrat defence spokesman, added: "This tragic death shows once again that British service personnel remain under constant threat in Iraq."
Mr Blair said he believed the past week had been a "particularly grim seven days" in Iraq but insisted the Allies' determination to prevail was undiminished. Geoff Hoon, the Defence Secretary, said it was "difficult to speculate" how many troops would be needed in Iraq this time next year.