Londoners pride themselves on their resilience: A day after the lethal July 7, 2005, transit system bombings that killed 52 commuters, many came back onto the streets and resumed their normal routines.
Still, some acknowledged an undercurrent of anxiety Sunday. Chris Denton, a 44-year-old engineer, said he had asked that his family not come out to support him because of a possible copycat attack. "I left them at home," he said, "if only for my peace of mind."
The men's race was won by Ethiopian Tsegaye Kebede; the women's champion was Kenyan Priscah Jeptoo.
A seemingly relaxed Prince Harry presented awards to the wheelchair racers and mingled with spectators.
"It's fantastic, typically British," he told the BBC. "People are saying they haven't seen crowds like this for eight years around the route. It's remarkable to see."
He said it was "never an option" for him to cancel his appearance following the Boston bombings.
"No one has changed any plans, volunteers, security, nothing has changed," he said. "Typically the British way."
On Blackheath, the spacious green common area where the race begins, runners massaged each other's legs as loud pop music boomed on a sound system. A half-dozen police officers in reflective vests mingled and chatted with the runners. Many in the crowd wore Boston T-shirts.
Moments before the majority of runners set off on the grinding course, announcer Geoff Wightman used the loudspeakers to ask for a moment of silence. He described marathon running as a global sport that unites runners and supporters in every continent in a spirit of friendship.
As those gathered responded to his call, the only noise that could be heard was the buzz of helicopters and the beeping of a truck.
Security was plentiful but not intrusive near the finish line at the Mall in front of Buckingham Palace. Marathon staff, officials and journalists had their bags checked, a process not deemed necessary at the event last year. Officials said this was in response to the Boston attack.
Marathon organizers plan to donate money to a Boston fund set up to help the bombing victims. They said they did not consider canceling the London event, which is a highlight of the sporting calendar.