LONDON -- Britain fell silent Friday on the first anniversary of the suicide bombing assault on London's transit system -- a stunning strike that killed 52 commuters and wounded more than 700 in the capital's deadliest attack since World War II.
Prime Minister Tony Blair, survivors and city workers bowed their heads during two minutes of national silence observed from the Wimbledon tennis tournament to Scotland, a quiet punctuated by the solemn tolling of bells at St. Paul's Cathedral in the heart of London.
Mourners carried flowers and candles to makeshift shrines near the sites of the four bomb blasts. Reflecting the widespread feeling of unease that grips London, one person left a small note that read: "We will never forget."
"This is a time when our country unites across all races, religions and divides and stands in solidarity with all those who have suffered so much, in sympathy with them and in defense of the values which we share," Blair said at Fire Brigade headquarters.
Relatives of the dead gathered later for a tearful private ceremony at Regent's Park, some reading poems to honor their loves ones. Names of all the victims were read one by one as many in the crowd wept and people lined up to place yellow flowers in a mosaic memorial.
Britain had dealt with Irish Republican Army attacks for decades and had endured the bombing of a U.S. airliner over Lockerbie, Scotland, in 1988 that killed 270 people. But last summer's bombings plunged Britons into the new era of terrorism that began with the Sept. 11 attacks -- an act that had led Britain to become the strongest ally in the U.S.-led fight against terror.
Britain also was forced to examine the implications of its multiculturalism: All four suicide bombers were young British Muslims -- three born in Britain of Pakistani origin and one a Jamaica-born convert who grew up in central England.
One of the London bombers was shown in a video released Friday on the Internet, saying that non-Muslims in Britain had declared war on Islam.
Terrorism committed in the name of Islam has led many to wonder whether, in the post-Cold War era, the world is gripped by another clash of civilizations -- one in which the values of Western liberal democracies are in irreconcilable conflict with those of Muslims, whose numbers are growing across Europe.
The video released Friday added a new dimension to the secrets that died with the London bombers. Al-Qaida deputy leader Ayman al-Zawahri claimed in the video that two of the London attackers received training for a suicide mission at an al-Qaida camp.
For Londoners, the attacks have shaken -- but not entirely overturned -- a conviction that the two cultures can coincide peacefully in the vibrant multicultural capital that is their home. Still, the background of the bombers came as a shock to Britons.
"Today is a very sad day," said Paul Dadge, a computer technician who was pictured in newspapers around the world leading a bandaged survivor from the wreckage last year. "It is also a day to mark those people who lost loved ones and the survivors."
Residents woke to the sound of police helicopters hovering over the city Friday as some Londoners made a determined effort to continue their daily routine.
But at the same time, a sense of mourning descended on the city -- as well as apprehension at the knowledge that any repeat attacks had the potential to devastate the precarious security that the affluent, cosmopolitan city has regained.
Buses and subway cars were standing-room only during the morning rush hour. But the atmosphere on the Underground was tense and subdued, as the city was reminded of the 52 people who never made it to their destinations last July 7.
Memorial plaques were unveiled at each of the three Underground stations affected by the attacks.
Flowers also were laid at Aldgate station, the site of the first blast, when a suicide bomber detonated his explosives at 8:50 a.m., killing seven people. Candles were lit at the Edgware Road where a bomb exploded minutes later, killing six, and between Russell Square and King's Cross where a third bomb killed 26.
One of the most striking images of the July 7 attacks was the fourth blast that killed 13 people and ripped apart a No. 30 bus near Tavistock Square.
"I can remember exactly what I was doing this time last year. Everything was all normal and then suddenly, it was not. People were going about their normal daily business and then bombs were going off," said Angelina Alcorn, 26, a nurse at University College Hospital who helped many of the injured from the final bomb.
"I will never forget the image of that bus. It is stuck in my mind," Alcorn said.
The bus driver, who survived, laid a large wreath of pink and white carnations, roses and lilies. On the card, he wrote: "You will never be forgotten. May you rest in peace. George Psaradakis. No. 30 bus driver."
Londoners were further rattled last July 21 by a botched bombing attack, then police fatally shot an innocent Brazilian when officers mistook him for one of the men suspected of planning the failed bombings.
People remain on edge -- even more so with the release of a video Thursday showing one of the four suicide bombers warning of more attacks. It was unclear how the video was obtained or how soon it was made before the attacks.
"What you have witnessed now is only the beginning of a series of attacks that will continue and increase in strength," said Shehzad Tanweer, 22, whose backpack bomb killed six people and himself aboard a Circle Line subway train near the Aldgate station in east London.
Terence Clark went to King's Cross station to remember his 27- and 31-year-old cousins who died on a Piccadilly line train.
"Why did they have to show the video last night?" he asked. "Why can't they leave us in peace? We lost our loved ones and we are serving a lifetime sentence."
The bombers -- Tanweer, Mohammed Sidique Khan, 30, Hasib Hussain, 18, and Jamaican-born Germaine Lindsay, 19 -- all grew up in the Leeds area, an ethnically mixed region about 200 miles north of London.
Some residents in the community warned journalists to leave Friday, while others said the area was still trying to heal.
"People are more intentional about who they know and who they befriend, but they are now building strong networks with people who they wouldn't normally know," said Ed Carlisle, 27, a resident of Beeston, where all of the bombers except Lindsay grew up.
Norman Kember, a British peace activist who was held hostage for four months by militants in Iraq, said he hoped sorrow over the attacks can bring people closer together.
"Although it is a terrible tragedy for the families, I am hoping that something positive may come out of it by building bridges across communities," Kember said.
Since the attacks Muslims have complained they are unfairly targeted because of their looks and religion.
"After the Sept. 11 attacks, I cried nearly every day when people refused to get in my car because I am Pakistani," said Idris Raja, a taxi driver who has lived in Britain 41 years. "After last year's attacks, people did the same thing. We're judged by a different set of standards."