London Marathon will be biggest in event's history
Around 37,800 runners will tackle today's Virgin Money London Marathon, making it the biggest in the event's 35-year history.
That compares to the previous record of 37,227 set in 2012.
Watching them will be an estimated 750,000 spectators who will line the streets of the capital as world record holder Paula Radcliffe participates in her final competitive marathon.
The 41 year old will start at the head of the massed ranks rather than the elite field.
Everything you need to know about the London Marathon 2015
Her women's marathon world record of 2:15:25, set in London in 2003, is almost three minutes faster than any other woman has ever run.
In the men's race Wilson Kipsang will bid to become the fourth man to win three London titles, while Britain's Paralympic champion David Weir is aiming for a seventh London wheelchair title.
Fortunately for them, the forecast is good with just patchy rain and mild temperatures for the 26 miles.
Met Office meteorologist Mark Wilson said the weather should not present any problems.
"It's not looking too bad," he said.
"It will be a cloudy morning with some patchy rain on and off throughout the morning. The rain doesn't look like it will be very heavy.
"Through the afternoon it should turn generally dry with some light afternoon brightness.
"Temperatures will be fairly mild so around 8C for the run which is not so good for the spectators standing on the side of the road but pretty good running conditions."
Five politicians are taking time off from election campaigning to pound the streets of London, including four Conservatives - minister for children and families Edward Timpson, Wales Office minister Alun Cairns, Graham Evans and Richard Drax - and Labour's shadow justice minister, Dan Jarvis.
As usual a host of celebrities will also tackle the course to raise money for charity.
They include Formula One driver Jenson Button, Radio 1 DJ Greg James, TV presenter Jenni Falconer, fashion designer Henry Holland, Made In Chelsea star Oliver Proudlock and US model Christy Turlington Burns.
The oldest entrant is Paul Freedman, 90, from Hornchurch, Essex, while the youngest will be Jonny Innes from Falmouth, Cornwall, who is celebrating his 18th birthday today.