Nobody claimed responsibility for the latest plot, and government security officials said late yesterday that no suspects have been identified.
As police searched for car bombs and terrorists in the city of 7.5 million, roads were closed and police sirens echoed. Authorities stepped up security across Britain, from central London streets to the Wimbledon tennis tournament.
But Londoners -- who have experience in dealing with bombs and terrorism -- were not in hiding and the West End was bustling again by nightfall yesterday.
"I know you can't live your life being scared," Natalie Huntley, 28, a tourist from Adelaide, Australia, said outside St. Paul's Cathedral even as police investigated another suspicious vehicle parked on nearby Fleet Street. "You've just got to keep going, don't you?"
Authorities said the bombs in both cars were similar and that each had been abandoned in the same area near Piccadilly Circus. Had they exploded, hundreds of people might have been killed.
The discovery of the car bombs before they exploded allowed police to check for fingerprints and DNA clues, as well as other trace evidence. They also had footage from closed-circuit TV cameras, hoping the surveillance network that covers much of central London will help them track down the drivers.
The CCTV footage would be compared with license plate recognition software, Peter Clarke, British antiterror police chief, said. There are 160 security cameras in the Westminster Council, the district encompassing Piccadilly Circus and the Haymarket area, alone.
The discovery of the second bomb, about 20 hours after the first, suggested a coordinated and more sophisticated plot than was initially thought -- similar to the 2005 suicide bombings in which four bombs exploded within an hour of one another on London's transit system.
Some analysts said the bombers could be trying to send a message to Britain's new leader.
"It's a way of testing Gordon Brown," said Bob Ayers, a security specialist at the Chatham House think tank. "It's not too far-fetched to assume it was designed to expedite the decision on withdrawal [from Iraq]."
After the first bomb was announced, Brown said "we face a serious and continuous security threat in our country."
