A record number of runners have completed the London Marathon after sweltering in unseasonal heat.
St John Ambulance said it treated 5,032 people, and of these 73 were sent to hospital for further treatment.
The 36,391 runners were the usual mix of professionals, amateurs and celebrities, most of whom were raising money for charitable causes.
Temperatures hit 21C at midday, equalling the 1996 record, and rose slightly higher in the afternoon.
Celebrity chef Gordon Ramsey was among a number of famous faces to run - and suffer - in the heat.
"It was like running in a desert today. I stopped to help one guy. It was quite bad. They were dropping like flies," he said.
Other competitors included model Nell McAndrew, Olympic hurdle champion Sally Gunnell, wheelchair basketball player Ade Adepitan and rugby star Matt Dawson.
Michelle Dewberry, winner of the BBC television show The Apprentice last year, said she saw someone who had collapsed being resuscitated after about four miles.
She said: "I have seen lots of people passed out and being resuscitated. It is scary, scary stuff."
Matt Dawson, a members of England's rugby World Cup team, said the conditions were "brutal".
"I have seen it has really had an effect on some people. It just stops you in your tracks when you see people pass out in front of you," he said.
Kenya's Martin Lel won the men's race in an upset for favourites Haile Gebrselassie and reigning world marathon record holder Paul Tergat.
Runners were advised to drink water frequently
The UK's number one, Jon Brown, withdrew because of sickness.
Favourite Chunxiu Zhou from China won the women's race, while Briton Dave Weir retained his wheelchair title.
The St John Ambulance first aid charity provided some 1,400 volunteers, 50 ambulances and 59 treatment centres for the race.
Earlier, London Marathon chief executive Nick Bitel said that more than 100 doctors were out on the course, including some of the world's leading medical experts.
Organisers installed four run-through showers along the route and added an extra 2,600 bottles of water to the normal stock of 25,000 bottles at each station to help runners deal with the high temperatures.
Firefighter Garry Speakman, from Manchester, hopes to break the record for the fastest marathon in full fire uniform.
And Londoner Angus MacFadyen set a Guinness World Record for the fastest marathon on crutches.
The 35-year-old could only use his right leg and 'hopped' round in a time of 7 hours and 17 minutes.
He also raised more than £14,000 for the No More Landmines charity - £6,000 of which was donated after he appeared on television on Sunday morning.
"It was an amazing day and a thrilling experience but an absolutely exhausting one as well," he said.
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