Olympic champion Adam Peaty claimed an expected title and Ben Proud a surprise gold medal at the World Championships in Budapest on Monday.
Peaty bettered his own championship record to finish in 57.47 seconds in the 100 metres breaststroke, but his own world record of 57.13secs set last August in winning Olympic gold in Rio was beyond him.
His nearest rival was Kevin Cordes of the United States, who was 1.32 seconds behind, while bronze went to Kirill Prigoda of Russia in 59.05.
Briton Ross Murdoch was eighth in 59.45 as Peaty retained the title he won in Kazan, Russia two years ago.
After Peaty had received his medal, Proud won the 50m butterfly in 22.75 seconds.
He had qualified fourth fastest, but built on a superb start to touch the wall first.
Peaty said: "I went out there with a lot of guts tonight. If you want to go 56 you're going to have to do stuff you've never done before and I was out in a 26.5 - that was very, very easy.
"I'm still 1.5 seconds ahead of the rest of the world, I'm very happy with that.
"It's not the time, it's the way I did it. Not many people can go out on 26.5 and come back. Only me has been under 26.6 in the world on just a 50.
"The way I swam it is very encouraging for me for the future."
