The race was preceded by 30 seconds of applause for Kelvin Kiptum, 2023 winner of the men's race, who was killed in a car accident in February. A poignant day ended with two more Kenyan victories, with Jepchirchir in particular putting down a marker ahead of her defense of her title at the Paris Olympics.
The field for the women's race was considered one of the best ever assembled, with three of the four fastest women in history competing. The 30-year-old Kenyan came home in front of world record holder Tigst Assefa and Joyciline Jepkosgei to break the record mark without male pacemakers.
Jepchirchir's time of 2 hours 16 minutes 16 seconds smashed the women's-only course record of 2:17:01 set by compatriot Mary Keitany in 2017. Retired British star Paula Radcliffe ran a time of 2:15:25 in a mixed-sex marathon in London in 2003, using male pacemakers.
"I was not expecting to run a world record," said Jepchirchir. "I knew it might be beat, but I did not expect it to be me."
"I am so happy to qualify for the Olympics and I feel grateful. I'm happy to be at Paris, and my pray(er) is to be there and run well to defend my title. I know it won't be easy, but I'll try my best."
Munyao got the better of Ethiopian legend Kenenisa Bekele to take the men's race in 2:04:01. A three-time Olympic gold medalist on the track, Bekele was on course for his first win on the streets of London aged 41, but Munyao proved too strong in the closing kilometers to pull clear up London's famous landmark The Mall towards the finish line.
"At 40 kilometers I got some pressure from Bekele, but I had a lot of confidence because I trained for this race," said Munyao. "After 40 kilometers I thought I had enough energy to win. That's why I kicked, and I knew I would win."
The 27-year-old also paid tribute to Kiptum, whose sudden death sent shockwaves through the sport. "I think about him and let him rest in peace. He came here in London and he won."
Behind the front two, it was a great day for the British duo of Emile Cairess and Mahamed Mahamed as they finished third and fourth respectively to close in on a place at the Paris Olympics.
A record number of people are running the 26.2-mile (42 kilometer) route through the British capital, with over 50,000 participants taking part.
Among them is new Manchester United co-owner Jim Ratcliffe, who faces a race against the clock to finish in time to see his side take on Coventry in the FA Cup semi-final at Wembley later on Sunday.