Kenya's Joyciline Jepkosgei wins fast women's race in 2:17.42, world record holder Brigid Kosgei fourth
Ethiopia's Sisay Lemma goes clear to win men's race in 2:04.01
Junior doctor Phil Sesemann seventh on marathon debut; Charlotte Purdue first GB woman to finish in 10th
Switzerland's Marcel Hug and Manuela Schar set course records to win wheelchair races; Britain’s David Weir third in men's race
Event returns to traditional course and with charity runners for first time since 2019
More than 36,000 on London's streets, with 40,000 participating virtually
Purdue is around 40 seconds behind the leaders, running with Australian Sinead Diver and pacemaker Eilish McColgan.
In the men's wheelchair race, leaders Marcel Hug and Daniel Romanchuk have just passed the Cutty Sark. David Weir was on his own for a bit but has now managed to find a group.
In the women's wheelchair race, Manuela Schar is going at course-record pace up front.
Charlotte Purdue became the fourth-fastest British female marathon runner ever when she finished in 2:25.38 in 2019.
She is looking to trim that time even more this year, with London becoming even more significant than usual after she missed out on selection for the Olympics.
"It took me a bit of time to get over it because it is such a big thing and I was aiming for it for so long," she told BBC Sport.
"I was really annoyed and angry but as soon as I had London as a focus I just channelled all my energy into London. It was nice to have that as a big goal and something I could get excited about.
"Now I’m all in on this race. A PB would be a great result and top 10 would be nice."
Image source, Getty Images#bbcmarathon or 8111 on text (UK only - texts will be charged at your standard message rate)
HeadteacherChat: I absolutely love the London Marathon. Good Luck and Well Done to everyone doing the 26 miles run today wherever you are!
Succeeding for Sandra: The BEST of luck to Julie taking on the London Marathon today for Muscular Dystrophy UK through Succeeding For Sandra! The build up hasn’t been ideal due to injury/an arthritis diagnosis but we’re behind you all the way!
Paula Radcliffe
Women's marathon world record holder on BBC TV
This leading group [in the women's elite race] can absolutely run at a slower pace in the first half and then push on and run at a substantial negative split in the second half.
It's an easier way to run a marathon, particularly on this course.
The leaders in the women's elite race, including Brigid Kosgei who is going for a third successive victory, have made a relatively slow start.
Kosgei won marathon silver at the Tokyo Olympics not long ago so it's understandable that she wouldn't have much in the tank for a fast race today.
Baroness Tanni Grey-Thompson
Eleven-time Paralympic champion on BBC TV
This is a really miserable place for David Weir to be in right now. He's doing enough to stay ahead of the chasing pack, but he might do better to actually drop back and work as three people together rather than on his own.
Marcel Hug and Daniel Romanchuck want to be clear of the field, they want to just play cat and mouse with each other.
#bbcmarathon or 8111 on text (UK only - texts will be charged at your standard message rate)
Julie Cozze-Young: Please give a shout out to my husband Tim Cozze-Young running his first London Marathon today. He is running for Dogs For Good UK.
David Weir has been left behind by the leaders in the men's wheelchair race, Marcel Hug and Daniel Romanchuck.
Weir has a tough task on his hands now. Twenty miles is quite a way to go on your own.
Manuela Schar has taken the outright lead in the women's race and is hunting down some of the men.
#bbcmarathon or 8111 on text (UK only - texts will be charged at your standard message rate)
Jane: I’m running today and trying to break the World Record for the fastest marathon (female) dressed as a 3-D Plant!!! Please give me a shout out and wave if you see me…that would be bloomin’ marvellous.
Dan: Good luck to Jack Peedell and Ruby Featherstone running for Brain Research UK and Dementia UK. You’ve got this Peedz!
And they're off!
It's set to be an extremely competitive elite women's race. We'll bring you more info on who to look out for shortly.
Kenyan world record holder Brigid Kosgei is aiming for a third successive victory in the women's elite race after emphatic wins in 2019 and 2020.
Germany's Katrin Dorre was the last athlete to complete such a treble in the women's race with wins between 1992 and 1994.
Kosgei will face stiff competition with Israel's Lonah Salpeter, the seventh-fastest woman over the distance, and Kenya's reigning New York City Marathon champion Joyciline Jepkosgei hunting a first London win.
Charlotte Purdue and Natasha Cockram, the first Briton in the 2019 and 2020 races respectively, are aiming to qualify for next year's World Championships in Oregon.
Image source, Getty ImagesMarcel Hug, who won four golds at Tokyo 2020, is heading up the men's wheelchair race currently with London favourite David Weir up in the front pack too.
Manuela Schar is leading the women's wheelchair race currently.
And in just three minutes' time the women's elite race will get going too. It's all happening!
#bbcmarathon or 8111 on text (UK only - texts will be charged at your standard message rate)
Georgie, Ruby, Poppy & Reggie: Good Luck Duncan Raison!!! We LOVE you! xxx
Anonymous: Good luck to my Amazing Step Daughter Lisa Napier running her 2nd London Marathon today in aid of Diabetes and in memory of her beautiful Dad John Wilkinson xx
Please remember to put your names on texts. Thank you!
The 2021 London Marathon is go! Hannah Cockcroft sounds the hooters and the wheelchair racers are off.
No sign of rain yet, here's hoping it holds off all day.
Image source, BBC SportOnce these wheelchair races are under way all the action will be coming thick and fast.
08:50 BST Elite wheelchairs
09:00 BST Elite women
09:30 BST Elite men and staggered mass start
BBC Two
Paralympic gold medallist Hannah Cockroft on BBC Two: "It's a massive honour to be here today, I never thought I'd find myself on this starting line.
"Shelly Woods is back in the race, I trained with Shelly and she trained so well, I can't wait to see what she's doing.
"She had her son just after the Rio Olympic Games, which she sat out of, but she's found her love for it again, she's found her passion. It's amazing to see her going out and racing.
"She did the quickest time she's done in ten years just last week. "
Image source, Getty ImagesThe wheelchair racers head to the startline to the cheers of the crowd. Eight-time champion David Weir is competing in his 22nd straight London Marathon.
But he says the prospects of him claiming a ninth victory in his hometown have receded as the technology beneath Swiss rival Marcel Hug has advanced.
Hug, 35, won four gold medals at this year's Paralympics in Tokyo using a specially designed chair that was developed for him over four years.
"I don't want to take it away from Marcel because he's a fantastic athlete and would probably have won a shedload of medals in Tokyo anyway," said Weir.
"But you can see he's got those extra gains from a Ferrari of a chair."
Weir says that Hug, who won the 2020 London Marathon, and American Daniel Romanchuk, who took the title in 2019, "are from another universe" in terms of speed.
Feeling inspired already? Here's how you can give it a go.
Couch to 5K: Get running half an hour in just nine weeks
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
You can watch by clicking play at the top of this page, or if you'd rather go down the traditional telly route all the details you need are below.
Network TV coverage
08:00-10:00 BBC Two and BBC iPlayer
10:00-14:30 BBC One and BBC iPlayer
Digital coverage
08:00-16:00 - uninterrupted coverage - BBC iPlayer, BBC Sport website and BBC Sport app
08:45-14:30 - elite races and finish line - BBC iPlayer, BBC Sport website and BBC Sport app
14:25-16:00 - finish line - BBC iPlayer, BBC Red Button and online
Highlights
18:00-19:00 BBC Two