LONDON — Paula Radcliffe needed exactly one year to go from novice to groundbreaker in the marathon.

She shattered her world best by almost two minutes yesterday — the biggest single drop in two decades — to win a second straight London Marathon, finishing in 2 hours, 15 minutes, 25 seconds.

“I don’t think any of us like to say we have reached the best, because you don’t know,” the 29-year-old Briton said. “You hope that you can keep running faster.”

Radcliffe never had competed at 26.2 miles until the 2002 London Marathon. Now she owns three of the four fastest women’s times in history, after lowering the world best she set just six months ago in Chicago by 1:53.

Catherine Ndereba of Kenya, Radcliffe’s predecessor as world-best holder, was second yesterday in 2:19:54. Deena Drossin of the United States was third in 2:21:16, five seconds faster than the American best set by Joan Benoit at Chicago in 1985.

“It was an impressive performance by Paula. I can’t wait to see the clips of it,” Drossin said.

Radcliffe’s performance overshadowed a thrilling men’s race. Olympic and world champion Gezahegne Abera of Ethiopia beat Stefano Baldini of Italy in a sprint. Abera and Baldini were each clocked in 2:07:56 after a finish that resembled a 100-meter dash. Joseph Ngolepus of Kenya was next, just one second back, followed by countryman Paul Tergat.

The winning time was two minutes off the world best.

The women’s marathon world mark has been broken four times in the last 2 1/2 years and six times since 1998. Tegla Loroupe of Kenya set the standard of 2:20:47 five years ago, and the mark has fallen a total of more than five minutes since. Yesterday, Radcliffe lowered the world best by the greatest margin since Benoit clipped 2:46 off Grete Waitz’s mark at the 1983 Boston Marathon.

“There was a lot of pressure, and people were talking about the times I was going to run,” Radcliffe said. “I went through halfway way faster than I had planned to, even if I felt good.”

London Marathon organizers put eight male pacesetters into the women’s race, making it a “mixed” field eligible for world bests according to the IAAF, track and field’s governing body.

The race was run with light winds and a starting temperature of 50 that edged up to 60 by the finish.