Four British men inspired by al-Qaida blew themselves up on three London subway trains and a bus during the morning rush hour on July 7, 2005, killing 52 commuters and injuring more than 700. The memory of that morning remains raw in this country of 64 million.
Solemn ceremonies were held throughout the capital, starting at the memorial in London's Hyde Park devoted to the victims. Prime Minister David Cameron and London Mayor Boris Johnson weaved through the memorial's 52 pillars to lay wreaths, one for each victim.
At 8:50 a.m., the moment the attacks began, the park fell silent. Families of victims clutched flowers. Some in the crowd bowed their heads.
Sajda Mughal, a survivor, said even after 10 years, the anniversary remains "emotional."
"(The ceremony) drew me back to the very same day, when I experienced the whole traumatic event being down there in the Piccadilly line, hearing those screams, people banging on the carriage," she said. "And then, as I was watching the wreath being laid, I came back to 2015 and I thought 'Well, I am alive, thank God I'm alive.' But unfortunately, we've lost 52 lives."
Johnson said the attack was a terrible shock to the capital but it was important to remember it.
"The people who are trying to attack the city basically failed," he told The Associated Press.
The attack occurred two years after Britain took part in the U.S.-led invasion of Iraq. But former Prime Minister Tony Blair, the nation's leader at the time of the bombings, said Tuesday that terrorism was "a global problem" that affected countries regardless of their involvement in the war in Iraq.
Across the city, survivors, transport staff and emergency workers laid flowers at the sites of the four bombings. Some Londoners heeded a call to walk part of the way to work in memory of the day 10 years ago when the city's transit network stopped.
At King's Cross and other Underground stations, the trundle of luggage wheels stopped as staff and passengers paused for a moment of silence at 11:30 a.m.
Among them were paramedics David Tompkins and Drew McRae, some of the first crews to reach the bombed Piccadilly Line train where 26 people were killed. McRae remembered the eerie silence, while Tompkins recalled the "unbearable" heat.
"In 15, 16 years, no call has ever come close to that," Tompkins said.
"And hopefully nothing ever will again," added McRae.
Cameron said the slayings last month of 30 British tourists in Tunisia was a reminder that terrorist threats remain real and deadly. The gun rampage in the Tunisian resort of Sousse was the deadliest attack on Britons since 2005.
"It's a day when we recall the incredible resolve and resolution of Londoners and the United Kingdom, a day when we remember the threat that we still face," Cameron said. "But, above all it's a day when we think of the grace and the dignity of the victims' families for all they have been through. And we honor the memory of those victims and all those that were lost 10 years ago today."
Jill Lawless contributed to this story.