The Team GB quartet including Scot Kathleen Dawson and Peaty set a world record in a gripping final of the inaugural mixed 4x100 metres medley relay. It was a second gold of the Games for Peaty and James Guy and the first for Dawson and Anna Hopkin. It was also the fourth British gold in the pool to accompany two silvers and one bronze, matching the exact haul they achieved 113 years ago in London with the prospect of more to come on Sunday.
Their achievements represent a massive turnaround from when British Swimming's funding was slashed after a failure to win a race at London 2012.
"I hope this team and the rest of British Swimming get the recognition and the respect that they deserve because it's been f*****g hard," said Peaty, who retained his men's 100m breaststroke title earlier this week. "It's the only way to get the emotion across. Honestly people don't understand how hard it is. Hopefully people back home can understand that.
"I've been doing this for seven years since 2014 and I didn't think the team would be where they are today. You've got such amazing talent. It's just incredible to be part of that and hopefully people back home are pretty pumped."
Peaty will be eyeing a fourth Olympic gold and third in Japan this week in the men's 4x100m medley relay final on Sunday, but he feared the worst on Saturday morning after thinking Guy had jumped in too early at their handover.
Britain jumped from sixth to fourth at the halfway stage after Peaty's incredible breaststroke split of 56.78 seconds before Guy catapulted them to top spot with an equally astonishing time of exactly 50seconds in the butterfly.
But Guy himself worried he had set off a fraction earlier and did not allow himself to get carried away with the celebrations until he knew he would not get disqualified.
"As soon as I dived in I'm thinking 'I've gone too early, I've screwed it up, I'm going to get a DQ, but you know, it's too late now, just go for it'. Afterwards I was just waiting and just saying 'please, please, please, please...'"
The event has been added to the Olympics schedule for the first time - where two males and two females must be selected but the nation can use any combination in the backstroke, breaststroke, butterfly and freestyle splits.
Dawson did not get off to an auspicious starts after slipping in her push off the wall in a leg where she was up against four males, including the 100m and 200m backstroke winner Evgeny Rylov of the Russian Olympic Committee.
Britain were six seconds off the pace when Peaty entered but the 26-year-old and Guy helped their nation into a lead of six tenths of a second as Hopkin anchored their race in the freestyle.
Hopkin came into the race going head-to-head against the men's 100m freestyle champion Caeleb Dressel but the American was well back as Britain touched out in three minutes 37.58 seconds.
China took silver, 1.28 seconds behind the winners, while Australia collected bronze.