But as CBS News Correspondent Allen Pizzey reports, the city that has prided itself as being a haven for those seeking a better life has become a place of suspicion and fear.
Terrorism expert Martin McCauley says that the city can no longer be perceived as a safe haven for Islamic radicals.
"Some people maintain because London and Britain has been very liberal in its asylum laws and very many Islamic radicals have entered Britain that in fact London would be protected," says McCauley. "That myth has now been exploded."
The British police method of watching but not acting against radical Islamic firebrands like cleric Sheikh Abu Hamza until they actually committed a crime made it difficult to pre-empt attacks. Some experts, like defense expert Dominic Armstrong, believe it will get even harder now that the call to jihad has been answered.
"They might have been sleepers for a number of years here," says Armstrong. "We've had open borders and we have a very open policy and it's easy for people to travel in and out of this country."
There are plenty of places in London where radicals can become just another face in the crowd.
Long-established immigrant communities face a nervous future. They worry that radicals may be hiding in their midst--as invisible to the law-abiding residents as they are to the security authorities.
But Prime Minister Tony Blair was quick to try to build a united anti-terrorism front.
"We know that these people act in the name of Islam," said Blair. "But we also know that the vast and overwhelming majority of Muslims here and abroad are decent and law abiding people who abhor this act of terrorism."
Immigrants in London say they consider themselves "Londoners first." Community leaders such as Dalawar Chaudry told Pizzey that they are as far from radical Islamists as any other Briton.
"Unfortunately we all get painted by the same brush and it's a very dangerous thing to do," says Chaudry. "We don't know who's responsible for this act."
The city that prided itself as being a haven for those seeking a better life has tonight become a place of suspicion and fear.