Three-time winner Paula Radcliffe said the "magic of the London Marathon" helped her finish as she ran the race for the last time competitively.
Briton Radcliffe, 41, ran the 26.2-mile course in two hours 36 minutes 55 seconds, less than three years after surgery on a serious foot injury.
"It was just amazing the whole way round," the world-record holder said.
"I wore the sunglasses to keep a lid on my emotions and they definitely hid some tears along the way," she added.
Radcliffe won the London Marathon in 2002, 2003 and 2005, and her 2003 winning time of 2:15:25 remains the world record.
A foot injury in 2012 ruled her out of the London Olympics and she feared she would never run again after surgery in August of that year.
Her participation in this year's race was in doubt when she injured an Achilles in training, but, cheered on by thousands of fans, she finished the course.
"I came into this race unprepared and hoped the magic of the London Marathon would help me and I'm sure it did," she said.
"Down the last mile I thought 'I don't care about the time', I just wanted to thank as many people as I could.
"I knew it would be emotional and it was so emotional. I nearly lost it at Birdcage Walk but the crowds bowled me over, I wanted it to last forever. It was so special, I'm really going to miss it.
"I was looking to finish holding hands with someone. I always wanted to run with my dad but never managed it so I did it in spirit instead."
The women's race was won by Ethiopia's Tigist Tufa, who sprinted clear to finish in 2:23:22, 18 seconds in front of Kenya's two-time London winner Mary Keitany.
There was a Kenyan one-two-three in the men's race as Eliud Kipchoge beat Wilson Kipsang, the 2012 and 2014 winner, with world record holder Dennis Kimetto third.