Olympic track champion Sifan Hassan uses stunning comeback to win debut at London Marathon

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 Ethiopian-born 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 24-kilometre 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 30-year-old 5,000 and 10,000-metre 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 23-year-old Kenyan set the course record in 2:01:25 and just missed Eliud Kipchoge's world record