Kendra Harrison breaks 28-year-old world hurdles record at Anniversary Games

American Kendra Harrison broke a 28-year-old world record in the 100m hurdles, clocking 12.20 seconds at the London Anniversary Games.

Harrison, 23, was already the fastest woman in the world this year, but will not be at next month's Olympics after finishing only sixth in the US trials.

The previous world record of 12.21 had stood since 1988 and was held by Yordanka Donkova of Bulgaria.

Britain's Tiffany Porter came sixth and Jessica Ennis-Hill last.

"After not making the Olympic team I wanted to come out here and show what I could have done," an emotional Harrison told BBC Sport.

"The US team is the hardest to make, our country wants the top three from the trials and I was not that person. The pressure got to me on the day. I wish I could re-do that day.

"I came out here with a lot of vengeance. I knew I had it in me.

"I've still got a lot left in me, I'm definitely going to try and drop that time this season."

Harrison has run six of the seven fastest times this year, and two of the four fastest ever.

Defending Olympic champion Sally Pearson will also miss out in Rio after tearing a hamstring last month.

Four-time Olympic champion and BBC Sport pundit Michael Johnson said he had "never seen a race like that".

He added: "That record stood for 28 years, and could stand for another 28 years.

"She was almost a hurdle ahead of a world-class field. So much can go wrong in a hurdles race but she was flawless.

"I am so happy for her because it would have been a long difficult summer with her not going to Rio, but that world record makes up for it."

Ennis-Hill, who will defend her Olympic heptathlon title in Rio, ran a season's best 12.76 in her heat but had to settle for eighth in the final after clattering a hurdle.

"I'm so happy to run a season's best and it makes me confident with Rio next," said Ennis-Hill.

"I would've liked to have gone quicker in the final, but just smacked a hurdle really bad and lost all momentum and that was it."

Ennis-Hill's second run was still quicker than her prior season's best of 13.10, while her earlier performance was the second best time of her career, slower only than her 12.54 set en route to London 2012 gold.

Porter recorded a season's best time of 12.70.