The Olympic champion Michael Phelps has broken the 100 metres butterfly world record, clocking 50.22 seconds to win the title at the US swimming world championship trials.
Phelps broke the previous record of 50.40sec set by Ian Crocker four years ago at the world championships in Montreal.
His tally of world records is now five, along with the 200 freestyle, 200 butterfly and 200 and 400 individual medley.
He'd won the 100 fly title at the Olympic Games in Athens and Beijing but hadn't been able to wrest the world record from Crocker.
