UPDATE 1-Athletics-Uganda's Nakaayi upsets the field to win women's 800 metres

Ugandan Halimah Nakaayi pulled off an upset to win the women's 800 metres title at the world athletics championships on Monday while favourite Ajee Wilson was left with another bronze as she ran out of steam with 100 metres left. Wilson, hoping to become the first American to win the world title over the distance, led for most of the race but was overtaken by Nakaayi down the final straight as the Ugandan won in a national record of one minute 58.04 seconds.

Raevyn Rogers, another American, also sped past Wilson to take silver. Wilson also won bronze in London two years ago. Caster Semenya, the titleholder and three-times champion, did not take part after challenging the IAAF’s recently-introduced testosterone regulations.

The South African lost her appeal at the Court of Arbitration of Sport (CAS) against the rules that mean middle distance female athletes with a high natural level of testosterone must take medication to reduce it. She then appealed to the Swiss Federal Tribunal which initially allowed her to continue competing while she awaited its final verdict but then reversed that decision after hearing from the IAAF, ruling her out of the championships.

Wilson had won six of eight races outdoors this season, including the U.S. title -- her 10th overall -- and Diamond League stops in Stockholm, Monaco and Birmingham and Brussels, making her the obvious favourite. The 25-year-old looked set to continue her dominance as she led from the start.

But, after having to fend off attacks during the first lap, she was unable to repel another from Nakaayi who sped past down the final straight to claim Uganda's first medal of the championships. Rogers then came storming out of the blue with a devastating finale to snatch silver. 

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