Joanna Hayes set a new Olympic record of 12.37 seconds to win 100m hurdles gold after the favourite crashed out.
Canada's Perdita Felicien came to grief at the first hurdle and took Russia's Irina Shevchenko with her.
The medal ceremony was delayed after the Russians protested and demanded a re-run. But the appeal was rejected.
Olena Krasovska of Ukraine took silver with a time of 12.45 seconds while America's Melissa Morrison came through for bronze in 12.56.
Felicien had been the pre-race favourite but walked away in tears, flinging her shoes to the ground in anger and frustration.
"The first hurdle came up, I reached for it way too much,"
"Before I knew it I was on the ground. I couldn't believe
it, there was no coming back. This is going to take four years to sink in."
The race had been one of the most open finals for years due to the absence of some of the pre-Games favourites.
American Gail Devers, Spain's Glory Alozi and
Jamaican duo Brigitte Foster and Delloreen Ennis-London all failed to make the final.