American Sanya Richards-Ross won the women's 400m Olympic title here on Sunday in a time of 49.55sec to end a 28-year gold drought in the event for the United States.
Defending champion Christine Ohuruogu of Great Britain finished second in 49.70sec while DeeDee Trotter of the United States took bronze in 49.72sec.
Richards-Ross, 27, became the first American to win the Olympic title since Valerie Brisco-Hooks in Los Angeles in 1984.
In a thrilling race, Richards-Ross came strongly off the bend to fight it out with Trotter while Ohuruogu finished with a stunning final burst.
However, unlike in Beijing four years ago it was not enough to see the Briton - who lives near the Olympic Park - to get past the 2009 world champion.
Richards-Ross, who is married to NFL defensive back Aaron Ross, shook her hands in celebration after crossing the line on realising she had gained revenge on her bitter rival for defeat four years ago.
Ohuruogu, also world champion in 2007, was distraught at the end because of the race she had run, although she graciously did a lap of honour.
"I was stunned, I was stunned," she said.
"I was heartbroken actually ... to lose your title like that.
"It was tough but Sanya is a worthy competitor and she ran a good race so I have to be happy with what I did. I could have been last."
Ohuruogu, who would have been the first to defend the title successfully since France's Marie Jose Perec in 1992/96, said that she had battled in vain to stop herself from tightening up at the end.
"I tightened up, I could feel my shoulders lifting," she said.
"It's really hard to control when you are under fatigue. I thought I still had some time but the line came too soon and I thought, 'no, it's gone, it's gone.'"
"I came here with one thing and one thing only in mind and that was to continue my reign as Olympic champion so I am a bit disappointed. "