About 38,000 runners will take to the capital's streets on Sunday for the 36th staging of the London Marathon.
The millionth finisher in the history of the race, which was first held in 1981, will cross the line on The Mall.
The winners of the men's and women's races from 2015 - Eliud Kipchoge and Tigist Tufa - return this year.
Live coverage on BBC One begins at 08:30 BST and there will be commentary on BBC Radio 5 live, as well as live text on the BBC sport website.
As in many previous years, the field of elite athletes has a strong Kenyan presence.
Kipchoge and Wilson Kipsang provided a thrilling finish 12 months ago, with Kipchoge outsprinting his countryman up The Mall to win the men's race by five seconds.
Dennis Kimetto came third to complete an all-Kenyan podium. All three are strongly tipped to be involved at the business end again on Sunday.
In the women's race, Ethiopia's Tufa was a surprise winner ahead of Kenya's two-time champion Mary Keitany.
They resume battle this weekend, with Keitany joined by high-quality compatriots Gladys Cherono, the winner of the 2015 Berlin Marathon, and Florence Kiplagat, who won last year's Chicago Marathon.
Nice weather for a run?
Runners may have to battle snow for the first time since the race was inaugurated in 1981.
Forecasts suggest an icy spell is due to hit the capital over the weekend, but temperatures are not expected to be low enough for any snow to settle.
Still, that has not stopped one bookmaker offering odds of 100-1 for the race to be cancelled.
Holmes under the hammer
While celebrities taking their place on the start line is nothing new, few will face the expectations of Dame Kelly Holmes.
The only British woman to win two track gold medals at the same Olympic Games is 1-4 favourite to record the best time of the all the famous participants, ahead of former rugby union international Shane Williams, Games of Thrones actress Natalie Dormer and Birmingham City manager Gary Rowett.
"I'm hoping I just run round but if I end up having to walk for whatever reason then I'm going to have to deal with that," said Holmes.
"When I'm going down The Mall, I'll be sprinting like Usain Bolt and I'll be so proud of myself."
Other celebrities taking part include Radio Two's Chris Evans, The Only Way is Essex's Bobby Norris and TV personality Judge Rinder.
Running the Marathon at 88
Bedford grandmother Iva Barr, aged 88, is the oldest competitor in this year's race.
She has been running marathons for "30-odd years" and took part in the first race in 1981.
Her advice? "A good pair of shoes, nice comfortable clothes and start as slowly as you can - not much more than a fast walk - and then build it up from there."