Adam Peaty won the 100m breaststroke at the World Championships on Monday night and returned on Tuesday morning to qualify fastest in a world record over 50m.
The 22-year-old set the world record of 26.42 seconds en route to winning 50m breaststroke gold in Kazan, Russia two years ago.
Peaty was optimistic of going quicker in the non-Olympic event after a halfway split of 26.50secs in the 100m, which he had also won in 2015.
He predicted "something special" and delivered - clocking 26.10 in the morning heats.
Cameron van der Burgh of South Africa was second quickest in 26.54. The 0.44 margin is huge over one length.
Van der Burgh, the previous world record holder, congratulated Peaty on his world record.
"It's a good time, but gold medals aren't won in the heats," Van der Burgh said.
"We know what he's capable of now. He's shown all his cards. But it's a great swim nonetheless."
