Sifan Hassan completed a stunning comeback to win the women's race of the London Marathon after appearing to be injured part way through her event debut on Sunday.

The Ethiopianborn Dutch athlete triumphed in two hours 18 minutes 33 seconds in what was billed as possibly the strongest field ever despite falling off the pace and clutching her hip around the 24kilometre mark.

"I never thought I would finish a marathon and here I am winning it," said Hassan. "I had a problem with my hip, which made me stop. But it started to feel a little bit better. And then I missed one of the drinks stations!

"I didn't practice that part of the race because I have been fasting [during Ramadan] and so that was quite difficult."

The 30yearold 5,000 and 10,000metre Olympic champion then reeled in the leaders with 4.8 km remaining.

Hassan also overcame making a mess of collecting a drink from a water station, and even offered last year's winner, Yalemzerf Yehualaw, a gulp from her bottle.

Hassan pulled away from Alemu Megertu and reigning Olympic champion Peres Jepchirchir in a sprint finish along The Mall.

Earlier, women's world record holder Brigid Kosgei was forced to pull out less than four minutes after the start.

The Kenyan runner came into the race with injury concerns and looked in visible discomfort early on.

Kosgei, who holds the women's record of 2:14:04 limped to the sidewalk after around three minutes. She then bent down to untie the laces on her running shoes and signalled that her race was over.

In the men's race, Kelvin Kiptum collapsed to the ground after winning in the second fastest time in history over the distance.

The 23yearold Kenyan set the course record in 2:01:25 and just missed Eliud Kipchoge's world record by 16 seconds.

"I am so happy with the result," said Kiptum. "I don't know what to say right now, I am just grateful. The course felt good, there was a bit of rain around halfway, but it was OK.

"I enjoy doing the marathons, it is good preparation for me. I loved it; I am very happy."

In what was long distance great Mo Farah's final marathon, defending champion Amos Kipruto and world champion Tamirat Tola were also among the elite men's field that Kiptum left behind.

Farah, 40, finished ninth with a time of 2:10:28.

The marathon returned to its traditional April slot after three years of being staged in October due to the COVID19 pandemic.

A record 48,000 people were expected to cross the finish line near Buckingham Palace from a field of 49,675 runners who registered for the race.