Organisers of the London Marathon said on Wednesday that extra police would be deployed to monitor security at the event in the wake of the devastating fatal bombings at the Boston Marathon.
Security has been stepped up for Sunday's race after three people were killed and over 180 injured when two bombs were detonated as runners approached the finish line in the US city on Monday.
London Marathon chief executive Nick Bitel said the Mayor of London, Boris Johnson, had emphasised the importance of a visible police presence for the race in the British capital.
"We instigated a full security review. Considerable extra police and our own security resources will be employed," Bitel said.
"The Mayor made it very clear to the Commissioner (of the Metropolitan Police), and the Commissioner down to his staff as well, that it is about putting out the right number to send the right message.
"It is not about budget, it is not about money; it is about ensuring the police are able to do as they do every day and keep London safe and secure."
Organisers will have taken heart from the successful security operation put in place for the funeral of Britain's former prime minister Margaret Thatcher on Wednesday.
An extra 4,000 police officers took to the streets for the procession through central London, which passed off without major incident, despite fears of large-scale protests.
Bitel was reluctant to discuss specific details about the new security arrangements for the marathon but said he hoped the race would provide a symbol of unity after the horror witnessed in Boston.
"I am not going to get into precisely what those measures are because I think that is an aid to anyone who wants to do something," he said.
"I don't think they will. One of the great things about the London Marathon is that it is perceived as being this event that brings people together.
"One of the founding principles of the London Marathon was to show that at least on one day, humanity can be united."
A 30-second period of silence will be held before the start of the race in memory of the victims of the Boston attacks, while organisers are also encouraging competitors to wear black ribbons.
As yet, there have been no high-profile withdrawals from the event by elite runners, with British Olympic star Mo Farah among the top-level athletes scheduled to compete, although he is only running half the race.
Kenya's Wilson Kipsang, the 2012 London Marathon winner and Olympic bronze medallist, expressed sympathy for those caught up in the carnage in Boston.
"As an athlete, I would like to send our condolences to those people who lost their loved ones in Boston, especially at this time they are mourning. We know they are going through a hard time," he said.
"We are really sorry for what happened in Boston, but we should have no fear during the race (in London) because security matters will be put in place and we will run feeling free."
Geoffrey Mutai, who won the Boston marathon in 2011, said he had been deeply moved by what happened at this year's race.
"My reaction when I saw the news about Boston, I felt very sad because I know Boston," the Kenyan said.
"It was painful because those people who are there look like our families because we are together, we are runners. It was very sad for me."
Despite the new security measures, former London Marathon champion Paula Radcliffe said that she would have doubts about taking her family to this year's event.
"I think first and foremost, as a mother, I'd think more about having family at the finish area," the women's marathon world record holder told BBC radio.
"You put yourself there at your own risk but putting family in that situation is something people are going to have to come to terms with and conquer."