Four men accused of plotting to murder passengers on London’s transport network in the July 21 failed suicide attacks, appeared in court for the first time today.

The massive British police investigation into the July 21 London bombings is now centred on 13 people being held, Scotland Yard said tonight.

SCOTLAND Yard was last night engaged in its biggest ever operation as Britain’s top police officer warned the country faced a “campaign” of terror.

Scotland Yard Commissioner Sir Ian Blair today admitted further people could be shot as detectives hunt down the would-be suicide bombers who tried to bring further carnage to London last week.