Rutto broke away from compatriot Sammy Korir in the closing stages after both men recovered from a heavy fall -- the winner bringing down the runner-up -- on wet cobblestones three miles from the finish.

Rutto -- who made the fastest-ever marathon debut when he won in Chicago in October but who has yet to secure selection for Kenya's Olympic team for the forthcoming Olympic Games in Athens -- finished in an unofficial time of 2 hours 6 minutes 18 seconds.

Korir was second in 2:06:48 with last year's world champion Jaouad Gharib of Morocco third in 2:07:02.

"It feels great to be champion of London," said Rutto, who had cuts on his knees from the fall.

Last year's winner Gezahegne Abera failed to finish after suffering a recurrence of the Achilles tendon injury that forced him out of the world championships last August.

In the women's race Okayo won in extraordinary fashion. She set off at breakneck speed and appeared to have mistimed her run when she was passed shortly before the 11-mile mark by Romanian Constantina Tomescu-Dita.

But the diminutive prison sergeant, twice a New York marathon winner, recovered and regained the lead six miles from the finish before winning with something to spare in an unofficial time of 2:22:36.