Adam Peaty sliced more than three-tenths of a second off his own 50m breaststroke world record in the heats at the World Aquatics Championships on Tuesday.
Peaty swam 26.10 seconds in Hungary, eclipsing the 26.42 secs he produced at the 2015 Worlds.
The Briton, 22, retained his 100m breaststroke title on Monday.
“This morning I came in nice and relaxed. I wasn’t even up for it that much so it is crazy,” Peaty said.
“I wanted the world record but I don’t know if I wanted it in the heats. You can’t pick and choose but I am so grateful to be in front of that crowd,” he told BBC Sport.
The Olympic champion said he could break the record again in Tuesday evening’s semi-final with a time even closer to the 25-second mark.