Londoner Mo Farah finished second in the New York half-marathon, but he was led away in a wheelchair after crossing the finish line. The Olympic champion collapsed after completing the race 18 seconds behind winner Kenyan Geoffrey Mutai.
Farah fell over 5 miles into the race but recovered and quickly made up ground. The 30 year-old is preparing to make his full marathon debut in London next month.
There will be travel disruption due to the Royal Parks half marathon taking place today.
Road closures include Hyde Park Corner, Parliament Square, Victoria Embankment and Westminster Bridge, with a number of bus routes also affected.
TfL is advising drivers to avoid the area if at all possible as it has caused "serious delays" in the past.
Full details of the closures and how best to get around are on the TfL website here.
The Royal Parks half marathon takes in four of London's best known parks - Hyde Park, Kensington Gardens, St James’s Park and The Green Park.
The route began in Hyde Park at 9am, heading through Green Park and on past Buckingham Palace into St James' Park. It then moves across Embankment taking in the Houses of Parliament and the London Eye.
Finally it loops back round through Admiralty Arch and Kensington Gardens before finishing back in Hyde Park.
The Royal Parks half marathon is underway, with 16,000 people racing through four of London's best known parks.
The 13 mile route is expected to take a minimum of one and a half hours to complete by the fastest runners.
Nearly 100 sporting projectsin and around the capital have received a boost from the London Marathon Charitable Trust this year.
Grants worth more than £3.5million from the surplus made by the London Marathon organisation last yearhave been awarded in grants to 91 projects.
The largest award was made to the Ramgarhia Sports Club in Ealing to bring disused cricket facilities at Durden Park back into use, while the smallest went to Heathrow Gymnastic Club in Hounslow for additional fitness equipment.
Other large grants included: £150,000 for the regeneration of Copthall Playing Fields in Barnet; £150,000 for Holborn community centre in Camden; and £150,000 for a compact athletics facility at Stoke Newington School in Hackney.
The Boston tragedy will not put off spectators or runners taking part in tomorrow's London Marathon, the race's chief executive has insisted.
Security has been stepped up for the event, with a 40% increase in the number of police officers following the bombing of the Boston marathon.
The race's chief executive Nick Bitel said the enhanced police presence would help ensure the event will be "as safe and fun as it always is".
Scotland Yard said several hundred more officers will be out on the streets on Sunday, an increase of two-fifths on last year.
The world's oldest marathon runner has retired from racing.
101-year-old Fauja Singh completed his final race today, finishing the Hong Kong 10k race in 1 hour, 32 minutes and 28 seconds.
Mr Singh, from Ilford, East London, only began racing at the age of 89. He said he was happy to retire at the top of his game.
Bionic marathon runner, Claire Lomas, was presented with medals donated by other runners this lunchtime. Olympic gold medallist Matthew Pinsent presented her with the_ box of medals._Claire missed out on a real marathon medal as they are only given to people who complete the course in under 24 hours.
Earlier today Claire Lomas, who has just completed the London marathon, paid her respects at the spot where a runner died.
She stopped to pay tribute to Claire Squires, from Leicestershire, who died during last month's race.
It has taken Claire 16 days to complete the marathon.