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Video highlights - Coughlin defends her backstroke crown
American Natalie Coughlin made the most of a fast start to defend her 100m backstroke title in Beijing.
The 25-year-old Californian led from start to finish, touching the wall in 58.96 seconds.
Zimbabwe's Kirsty Coventry, who took Coughlin's world record in the semis, collected silver with American Margaret Hoelzer winning bronze.
Gemma Spofforth set a new British record of 59.38 secs but finished just out of the medals in fourth.
"Obvioulsy I'm disappointed," Spofforth, who is based in Florida, told the BBC. "I came here to win a medal but I came fourth.
"But it's my first Games and I'll look forward to 2012 now. I gave it all I could give and it's just disappointing to know that I came so close."
Spofforth will now turn her attention to the 200m backstroke heats on Thursday.
Coughlin, who has already claimed a silver in the 4x100 freestyle relay, will not contest the 200m back.
"It hasn't really sunk in yet," Coughlin said. "When I saw the clock I thought I had made a mistake and I only knew I had won when I saw the number one by my name.
"It's a great feeling, I am overjoyed."
Coventry, who set a new world record of 58.77 secs in the semi-finals, collected her second silver after being runner-up in the 400m individual medley.