Silence falls over London Marathon as thousands remember Boston London Marathon 2013 Security tight at London Marathon, first international race after Boston bombing 35,000 competitors observe 30-second silence in honor of victims Runners wear black solidarity ribbons to mark Boston attack For every person to finish race, organizers will donate $3 to Boston charity London (CNN) -- For a moment, the rustling costumes, nervous chatter, and jovial jostling come to a standstill. Silence falls over the 35,000 competitors who just minutes earlier had been impatiently rearranging themselves for the start of the London Marathon. For 30 aching seconds the spring sunshine beats down on their bowed heads, a sea of black ribbons pinned to their chests, as they remember those who never got a chance to cross the finish line. It is a deeply tender and haunting image, and unlike anything ever seen in the 32-year-history of the race. But then, this was never going to be just another London Marathon. Six days after Boston's Marathon was rocked by the bombing which killed three people and injured more than 180, the English capital hosts its own premier race. READ MORE: Tight security at London Marathon London is the first international marathon to follow Boston, and the attack which sent thousands of people scrambling in terror down smoldering streets and past upturned stands, looms large in the minds of competitors observing a silence ahead of the starting gun. The race comes after its director Hugh Brasher had urged participants in an e-mail Friday not to lose sight of what the London Marathon stands for. Police also appealed for anyone there to take extra care with their belongings, to avoid sparking security scare. WATCH: Boston wheelchair racer in London