Italy's Giorgia Bronzini beat Marianne Vos in the final few metres to win cycling's RideLondon Grand Prix.
Olympic silver medallist Lizzie Armitstead was third, ahead of Eileen Roe and British road-race champion and Olympic gold medallist Laura Trott, who finished fourth and fifth respectively.
"I really wanted to win in this beautiful city," said Bronzini.
"Women's cycling is full of power and we have nothing less than the men and we showed that."
In a show of strength across British women's cycling, seven of the top 10 finishers of the 1.3-mile lap race around London's St James' Park were British.
RideLondon attracted thousands of cycling fans to England's capital city, who were able to ride the courses the professionals compete on.
The event continues on Sunday when 2012 Tour de France winner and Olympic gold medallist Sir Bradley Wiggins competes in the men's Classic 100-mile Surrey to London race for Team Sky.
The event will be broadcast live on BBC One and online from 14:00 BST.