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Video - Gold for Coventry in 200m backstroke
Zimbabwe's Kirsty Coventry finally won a gold in Beijing with a world-record display in the 200m backstroke.
Coventry, who had won three silvers before Saturday's final, was always in control and powered home in two minutes 05.24 seconds to defend her title.
Margaret Hoelzer of the United States, who held the previous world record, took the silver while Japan's Reiko Nakamura won the bronze.
Britain's Lizzie Simmonds, 17, came sixth in a new national record.
Coventry had finished runner-up in the 100m backstroke and the 200 and 400m medleys.
She said: "I'm so thrilled. The plan was to go in and put everything on the line and see what I have to go home with," Coventry said.
"I'm excited to hear the national anthem play and for everyone back home to hear it.
"It's awesome. It was painful and my legs hurt a bit. It was my last race here and I wanted to give it everything.
"Getting the gold medal is the cherry on the top and it's such a relief."
Simmonds, who matched the leaders over the first length, said: "I got into the Olympic final and came sixth and I am delighted with that and to have swam so fast.
"Last year at the world championships I went 2:11 and today is almost three seconds dropped from there so that is fantastic.
"I feel like I am working my way up the ladder to the top."