The number of police officers on duty for the London Marathon has been boosted by 40% to provide reassurance in the wake of the atrocities in Boston, Scotland Yard said.
Chief Superintendent Julia Pendry revealed that there will be several hundred more officers out on the streets on Sunday, an increase of two-fifths on last year.
The senior officer, who has led the Marathon security operation for five years, said: "I have increased the number of officers for reassurance patrols by several hundred. It's about making sure that people who come to London on Sunday feel safe when they are in the city.
"It is a good 40% increase on last year on numbers of officers on the ground. We've got more search dogs out, we have got more on high visibility patrols."
Scotland Yard is in close contact with the FBI and Boston Police and there is nothing to suggest any link with the bomb attacks that hit the Boston Marathon on Monday.
Chief Supt Pendry said: "We're in touch with the Americans all the time. At this time there is no link whatsoever between the Boston Marathon atrocities and the London Marathon on Sunday. What we have got is a number of contingencies. I have several contingencies should anything change between now and Sunday; we can then react to anything that should happen.
"There is no link between the Boston Marathon and the London Marathon and there is no change to the threat level at this time to London. The thoughts of the Metropolitan Police service and our partners and our best wishes go out to the family and friends of the people in Boston."
Members of the public coming to the capital are being asked to make sure that they keep their belongings with them to avoid sparking security alerts.
"The message I'd like to give to everybody coming is that we want you to come on Sunday, enjoy coming to watch your family and friends race, but please look after your own belongings because unattended packages will cause us to have more work to do," Chief Supt Pendry said.
"Of course bring your bags, but please keep them with you."