American Brianna Rollins won the women's 100 metres hurdles title on Saturday on the eve of her birthday at the World Athletics Championships in Moscow.
Rollins, who turns 22 on Sunday, timed 12.44 seconds to take the gold, while defending champion Sally Pearson of Australia was second in 12.50sec and Tiffany Porter of Britain won the bronze timing 12.55sec.
Porter, who was born in America but three years ago was allowed to compete for Britain as she qualified through her English-born mother, led from the blocks with Olympic champion Pearson on her shoulder.
Pearson, whose season has been affected by a longstanding hamstring injury, managed to get her nose in front as the race entered its final stages but Rollins came powering through on her right.
Pearson still held the edge after clearing the final hurdle but Rollins, appearing in her first senior global final, had the speed in her legs to get upsides the 26-year-old Australian and dip to get the gold.
Rollins, who had signalled she would be a title contender despite her youth having run the fastest time of the year earlier in the season, said she had understandably felt nervous as they settled into the blocks.
"My nerves got the better of me initially and I didn't get the best of starts but I calmed down quickly and set Sally as my target," she said.
"It is alright to be nervous it is natural but it is how you react to that that makes the difference.
"To beat Sally in a world final is special as she is such a competitor and I am sure that my win will only serve to provoke her to want to regain her crown in 2015," she added.
Pearson said she was delighted with her medal given the tough season she has had.
"I have never been so happy to get a race over and done with. I am happy with the way the season ended up," she said.
"It's been very hard on me and my coach. This silver is going to be in the far distant past.
"We have had dramas and troubles. I did it all today for my coach, she's been there all the way for me.
"I haven't had the best of seasons. I am not 100 percent but these girls are and only one of them beat me. It shows what a real competitor I am."
Porter, who embarrassingly admitted in 2011 she did not know the words to the British national anthem a year after she was given citizenship, took her first medal for her adopted country as she held on to finish clear of America's 2008 Olympic champion Dawn Harper.
"I really believed in myself and my programme," said 25-year-old Porter, whose younger sister has opted to compete for the United States.
"I knew I could be competitive against these girls. I'm happy to come away with a medal."