Mary Keitany produced a devastating performance to win the women's race at the Virgin London Marathon today in a time only world record holder Paula Radcliffe has ever beaten on the London course.

The Kenyan made a dramatic burst after 15 miles to leave defending champion Liliya Shobukhova and a clutch of highly talented rivals in her speedy shadows. From that moment on, the unrelenting 29-year-old was away and clear, and she strode home alone in 2:19:19 to move alongside Irina Mikitenko as the equal fourth fastest woman in history.

After smashing the world half marathon record earlier this year, Keitany announced herself on the marathon stage in superb style, improving her lifetime best by nearly 10 minutes to become the 10th woman to go under 2:20.

"I am extra happy to win," said Keitany. "I trained very hard and today it paid off. I was very confident because I knew I was in good shape, I knew the course was flat and I knew the weather was good."

Behind her, Shobukhova rallied in the final stages to take second in 2:20:15, 10 seconds inside the Russian record she set in Chicago last year, while Edna Kiplagat added a place on the London podium to the New York title she won last year, finishing third in 2:20:46. It was nearly five minutes inside her PB and the best time ever for a runner in third place.

"Obviously, I'm disappointed to come second but I'm very happy I broke the Russian record," said Shobukhova, after suffering her first defeat since finishing third here on her marathon debut in 2009.

The defending champion was in evidence from the first strides, running at the fore of a tightly-packed bunch of 35 elite women who set off under overcast skies with light winds and near perfect temperatures of nine degrees.

Shobukhova immediately tucked in behind the pacemaker Iness Chenonge who had been asked to reach half way in 70 minutes. She was bang on schedule with a 5:22 opening mile.

Keitany also showed her intentions from the start as a leading group of 10 quickly opened a gap on last year's silver medallist, Inga Abitova, who was at the front of a large second group, 10 seconds back. British debutante Jo Pavey was also there, plus the Asian Games champion Zhou Chunxiu, the 2007 winner.

Up ahead, Shobukhova looked supremely comfortable as they passed through 5k in 16:18, right on the requested sub-2:20 pace. With her were Keitany, Kiplagat, Mariya Konovalova, and five Ethiopians - Askale Tafa, Atsede Baysa, Aselefech Mergia, Bezunesh Bekele and Aberu Kebede.

The pace dropped slightly through mile six and they passed 10k in 32:54 and 10 miles in 53:33 with Shobukhova still at the front. These nine crossed Tower Bridge, clocking 67:00 at 20k before passing half way in 70:38.

As Chenonge dropped away Shobukhova took the cue to push on. Immediately, Konovalova and Tafa slipped back but Keitany was now running shoulder to shoulder with the reigning champion.

The brilliant Kenyan was disappointed to finish third on her marathon debut in New York last November, and was clearly in no mood for a repeat here. With barely a glance at her opponents, she put her foot down between miles 15 and 16 and kicked away from the Russian like a middle distance runner coming off the final bend of a track.

Within one blistering five-minute mile her opponents were beaten. It was a devastating burst, and she followed it by running the next three miles in under 5:10.

Keitany ran alone through the long loop round east London's Isle of Dogs with her opponents now out of sight on the road behind her. She negotiated the twisting corners under Canary Wharf with ease and by mile 18 had stretched her lead to 27s.

Her 5k split between 25 and 30k was 16 minutes exactly - a hammer blow the rest simply couldn't match. She looked superb, striding out along Poplar High Street and turned to face west again with the City ahead of her.

It was certainly too much for last year's bronze medallist, Aselefech Mergia, who soon dropped out as Shobukhova, Kiplagat and Kebede became the leading chasers, but Kiplagat and Shobukhova soon shrugged off Kebede as they battled for the minor medals.

There was no catching Keitany, though. Despite letting her pace drop, she stretched her lead as the duo behind began to hurt, no doubt their pride bruised as much as their lungs.

As the temperature rose towards 14 degrees, the run-in was always going to be tough. But Keitany had time enough to enjoy the moment. She emerged into the sunshine on Victoria Embankment and pushed on for Westminster, passing 40km in 2:12:07.

She may have slowed a touch (her 5km split dipping to 16:42) but she was well clear. Turning into The Mall in glorious isolation, she sprinted for the line to record the quickest time in the world since Paula Radcliffe enjoyed her third victory here in 2005.

Keitany is now behind only Radclilffe, Catherine Ndereba and Mizuki Noguchi on the world all-time list. "I knew I could get my best time here," she said after becoming the first Kenyan winner since Margaret Okayo in 2004. "I knew this top field would produce a good time."

Behind her Shobukhova unleashed her famous finishing surge to take shake off Kiplagat along the Embankment. She'd predicted sub-2:20 here, and expected to win, but the World Marathon majors champion had to be satisfied with second place, her first marathon defeat in four races.

"I thought at first I would be able to catch Mary," she said. "But her speed was so fast. I knew she has great speed from the half marathon so I wasn't surprised. As soon as she went away I knew that I was already fighting for second place.

"Towards the end I knew I would be second, but I didn't think about the Russian record until I crossed the line."

Kiplagat was also satisfied. "When Mary attacked I tried to run as fast as I can, but she was already gone," she said. "I lost speed when Liliya went past me but when I saw my time at the end I couldn't believe it."

Bezunesh Bekele finished fourth in 2:23:42, just missing the medals again, as she had in 2010, while fellow Ethiopian Atsede Baysa was fifth in 2:23:50.

Yukiko Akaba finished sixth again, as she did last year, in a personal best of 2:24:09, surely claiming a spot on Japan's world championships team, while Mikitenko was seventh, in 2:24:24.

Pavey was the first Briton home in 19th, making a successful marathon debut in 2:28:23, well inside UK Athletics' world and Olympic qualifying standards.

It was a race of unprecedented quality as a record 22 women finished in 2 hours 30 or better, obliterating the previous best of 15.