Some 40,0000 runners are preparing to pound the streets of the capital as they run the 39th London Marathon, with money raised since the event began set to surpass £1 billion.
The event starts with the Elite Wheelchair race at 9.05am before the World Para Athletics Marathon Championships Ambulant Athletes start five minutes later, followed by the Elite Women at 9.25am.
The Elite Men’s race starts at 10.10am along with the British Athletics and England Athletics Marathon Championships and Mass Race.
Runners and racers are set for a chilly start before the tail end of Storm Hannah makes way for sunny spells, the Met Office said.
British Olympic champion Sir Mo Farah is aiming to win the Elite Men’s race despite tough competition from world record marathon runner Eliud Kipchoge, 34, from Ethiopia.
Britain's four-time Olympic champion, who called time on his track career to focus on road running in 2017, came third last year.
The 36-year-old is up against world record holder Eliud Kipchoge, the Olympic champion who holds the course record and is looking for a fourth win in five years.
Kipchoge’s marathon record stands at 02.01.39 while Sir Mo’s personal best is 02.05.11.
Farah's preparations have been marred by an extraordinary row with former distance star Haile Gebrselassie over an alleged robbery in the hotel owned by the retired Ethiopian.
Eight-time winner David Weir competes in the wheelchair race for the 20th consecutive year.
Amateur racers taking part range from a hero police officer who responded to the London Bridge terror attacks to the husband of EastEnders star Dame Barbara Windsor.
Former Wimbledon winner Amelie Mauresmo is one of many famous faces taking part.
Pc Leon McLeod, 31, hopes to raise £10,000 for PTSD999, the charity which helped treat his post traumatic stress disorder after the attacks.
Dame Barbara’s husband, Scott Mitchell, who turns 56 on marathon day, has already helped raise £100,000 for Dementia Revolution, the 2019 Charity of the Year for the event.
Official figures from the Virgin Money London Marathon say the event has raised a total of more than £955 million for charities since the first in 1981.
Event director Hugh Brashner said: “No other mass participation event comes anywhere near this kind of fundraising.”