Adam Peaty led home a British one-two to secure his third consecutive world 100m breaststroke world title in South Korea.
The 24-year-old clocked a winning time of 57.14 seconds in Gwangju, well ahead of team-mate and training partner James Wilby who held off the challenge of China's Yan Zibei to take silver.
But Peaty said afterwards he was disappointed not to have lowered his own world record after he became the first swimmer in his event to break the 57-second barrier as he recorded a time of 56.88secs in the semi-finals.
"This is still very special to me, winning a World Championship title and faster than I've ever done it before," said Peaty, who will defend his 100m Olympic crown in Tokyo next summer.
"It's obviously a little bit slower than [Sunday] night as I made a tiny little error with speed on the first 50 [metres].
"But I think the most important thing going into next year is I'm still learning about myself.
"I'm very happy. With that constant expectation I put on myself there is a little bit of disappointment in me, but I think that will fuel me for next year as I want to go even faster now."