Metropolitan Police officials said the ranks of the constables lining the course will be 40 percent larger than last year, mainly out of a sense of caution and to "reassure" the competitors and spectators.
Police said there was no apparent link between the bombing at the Boston Marathon and Sunday's long run through the British capital. Security will be beefed up, with several hundred additional officers and more dogs trained to sniff out explosives, police told the BBC.
The London Marathon was expected to include more than 35,000 runners who will make their way from Blackheath to the finish line not far from Buckingham Palace.
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