Britain's top counter-terrorism officer has resigned after his security blunder threatened a major anti-terror operation.
London Mayor Boris Johnson said he had accepted Assistant Commissioner Bob Quick's resignation with "great reluctance and sadness".
Meanwhile, searches are continuing at properties in Greater Manchester, Liverpool and Lancashire after 12 suspects were arrested in a bid to smash an alleged al Qaida terror plot.
Mr Quick's downfall came after he was pictured on Wednesday clutching sensitive documents as he arrived in Downing Street for a meeting with Prime Minister Gordon Brown and Home Secretary Jacqui Smith.
The documents showed top secret details of a major anti-terror operation in north west England. And the blunder meant a police operation to arrest the suspects had to be brought forward 24 hours.
As police targeted the suspects - who sources said were allegedly linked to al Qaida - Mr Quick released an apology to Met Commissioner Sir Paul Stephenson saying he "deeply regretted" leaving the document on show. Assistant Commissioner John Yates will replace Mr Quick as head of counter-terrorism.
Mr Brown defended the anti-terror operation and praised Mr Quick for his service to the force.
Speaking during a tour in Carlisle, Mr Brown said: "Let me first thank all of the police forces that have been involved in the arrest of the suspected terrorists.
"We have been investigating a major terrorist plot and we have got to act early. Our first concern is always the safety of the public. It is right that we took the urgent action that we did.
"I have spoken to Bob Quick and thanked him for his years of service. He has apologised for what went wrong. I have also spoken to Sir Paul Stephenson, the head of the Metropolitan Police, and said we expect this investigation to move forward."
