Double Olympic gold medallist Laura Trott sprinted to victory ahead of Hannah Barnes in the inaugural RideLondon Women's Grand Prix.
Trott, 21, finished a bike length in front of her rival in the 15-lap criterium event, held over a 1.3-mile street circuit in the capital.
"This feels like my event, I felt I had to win. I'm so glad I did," Trott said.
Trott's Wiggle-Honda team-mate Joanna Rowsell suffered a suspected broken collarbone following a last-lap crash.
Barnes's MG-Maxifuel Pro team had been driving the pace with two laps to go, but Trott was led out expertly by colleague Dani King as the riders contested a bunch sprint on The Mall.
This ensured there was to be no repeat of Barnes's controversial triumph in June's London Nocturne.
In that contest, Trott was originally awarded the spoils in a photo finish despite Barnes appearing to finish ahead.
Organisers later admitted Barnes did cross the line first, but she had broken the rules by celebrating while close to riders who were being lapped.
The 20-year-old was then reinstated in first place following a review of that decision by British Cycling.
Speaking about the RideLondon event, Barnes said: "It was a really hard race with attack after attack. I was always on my toes but I got swamped a bit towards the end and couldn't get through."
Previously on Saturday, the two-day cycling festival began with an estimated 50,000 amateur cyclists riding an eight-mile course through central London.
The men will be in action on Sunday, in the 140-mile Surrey Classic (12:45 BST), which will feature around 150 of the world's top male cyclists.