Brits pull off shock win

Jamaica's Novlene Williams had led from the start but was pipped on the line by powerful finishes from the unfancied Brits.

It was a dream comeback for Ohuruogu, the Commonwealth Games champion banned for a year for inadvertently failing to give her location to out-of-competition drug testers. Her Great Britain and possibly athletics career are threatened as - even though there was no implication that her technical offence meant she was taking drugs - any athlete found guilty of any doping offence is automatically banned by the British Olympic Association.

But the permanent ban was reduced on appeal and her Olympic ban under appeal, and the Londoner was given the chance to make a late bid for the GB team, the decision to allow her to qualify after missing the UK trials vindicated by Britain's first gold of the tournament.

Williams had come out of the blocks powerfully, pulled away convincingly and looked to have sewn victory up but, either side of her in the lane draw, the Brits brought out late finishes and respective personal bests of 49.61 and 49.65 to push her out at the death.

Ana Guevara of Mexico came fourth with Dee Dee Trotter the highest finishing US athlete in fifth.