The UK, and London in particular, continue to be at high risk of another terrorist attack, with police being forced to change their tactics constantly in an attempt to disrupt or thwart any attempt to follow up the London bombings, Peter Clarke, the head of Scotland Yard's anti-terrorist branch, said on Tuesday.

Thousands of police who were deployed to central London for counter-terrorist operations in July have returned to crime-fighting duties in their local units, and to forces outside the capital, according to Whitehall sources.