Tokyo, July 26, (dpa/GNA) - A dominant Adam Peaty won gold in the 100m breaststroke at the Tokyo Olympics on Monday, as Australia's Ariarne Titmus shocked American superstar Katie Ledecky to win the 400m freestyle and Margaret MacNeil won the 100m butterfly.
The US meanwhile won gold in the men's 4x100m freestyle relay.
Peaty became the first Briton to win consecutive Olympic golds in the same swimming event thanks to victory in 57.37 seconds, the fifth fastest time in the history of the event. He now has 18 of the 19 fastest times ever recorded.
"I'm so buzzed because that was the first," he said "You can do what you want all year round, you can do what you want in your own arena, your own backyard - it doesn't mean anything.
"It means everything here. No one thinks about times. Yes, it would have been amazing to finish on a world record, but it's not about that."
The 26-year-old, whose gold was the first for Britain in Tokyo at the time, handily dispatched Dutchman Arno Kamminga, the only other swimmer who has managed to step on Peaty's previously uncharted waters by clocking a sub-58-second swim.
Italy's Nicolo Martinenghi took home the bronze with 58.33.
Titmus defeated world record holder and Rio champion Ledecky of the US by 0.67 seconds with an Oceania record 3:56.69 minutes, her second gold, the day after success in the Australian 4x100m freestyle relay.
“It is the biggest thing you can pull off in your sporting career, so I’m over the moon," said Titmus.
"I’m trying to contain it as much as I can. I have a big programme ahead of me, but I can enjoy this afterwards."
China's Li Bingjie came distant third with 4:01.08, a new Asian record.
Ledecky, a five-time Olympic champion, had not lost an Olympic final before Monday. The 24-year-old American is also set to compete in the 200m, 800m and the newly introduced 1500m freestyle races in Tokyo.
"I can’t be too disappointed," said Ledecky. "It was my second best swim ever (over 400m freestyle). I felt like I fought tooth and nail and that’s all you can ask for.”
Earlier, reigning world champion MacNeil turned on the jets after finishing the first 50 metres in seventh position to touch the wall in 55.59, winning Canada's first gold medal at the Tokyo Games after taking silver in the relay. She also set an Americas region record in the process.
China's Zhang Yufei missed out on gold by just 0.05 seconds, while Emma McKeon of Australia won bronze thanks to an even smaller margin, 0.01 seconds, over fourth-placed Torri Huske of the US.
Sarah Sjostrom, champion in Rio and world record holder, placed seventh. Her participation in the Games was in doubt after she broke her elbow slipping on ice in February.
The US team of Caleb Dressel, Blake Pieroni, Bowen Becker and Zach Apple was just half a second shy of the world record with 3:08.97 in their relay win ahead of Italy and Australia.
Dressel is chasing a six-gold haul at the Games over three individual events and three relays.
The second session consisted only of heats as, unusually, the finals in Tokyo all come early in the Japanese day to suit American broadcasters.
Ledecky posted an Olympic record 15:35.35 seconds in qualifying first for the 1,500m final, a race she is expected to win by a distance.
She also topped the 200m freestyle heats, with Titmus fourth, while Italian great Federica Pellegrini had a scare but reached the semis 15th of 16 who advanced.
There was a similar escape for South African Chad Le Clos, champion in 2012, who took the last spot in the men's 200m butterfly semis. Hungarian world champion Kristof Milak topped the standings.
His compatriot Katinka Hosszu, champions in Rio, was a strong second in the women's 200m individual medley after disappointment in the 400m earlier in the Games. America's Kate Douglass was quickest.