Suicide bombers could well be planning an attack in Britain, the commissioner of the Metropolitan Police warned yesterday.

Sir John Stevens said the threat of a suicide attack had taken a "quantum leap" after a mounting number of bombings this year in Saudi Arabia, Morocco, Russia and Iraq.

Speaking as the second anniversary of the September 11 attacks in New York and Washington approaches, he said: "We are at the highest level of alert, I think, that we have ever been."