Great Britain equalled their best swimming medal haul at an Olympics after winning the inaugural mixed 4x100m medley relay final in a new world record time at the Tokyo Aquatics Centre.
The quartet of Kathleen Dawson, Adam Peaty, James Guy and Freya Anderson were more than two seconds clear of the rest of the field in the heats, setting a new European record, and Team GB eased to victory on Saturday morning.
Anna Hopkin replaced Anderson for the final freestyle leg here and touched out in three minutes and 37.58 seconds for Britain's fourth gold in the pool at Tokyo 2020 and seventh gong overall - matching their tally from London 1908.
The time was 0.83 seconds better than the previous best benchmark of 3mins and 38.41 secs - set by China last year - while they finished 1.28 secs clear of China, with Australia taking bronze.
This 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.
It means the lead can change hands multiple times as men and women can race against each other in the same leg of an event that was first introduced for long course swimming at the 2015 World Championship.
Dawson started with the backstroke and her time of 58.8s meant Peaty leapt into the pool with Britain sixth, and the 100m breaststroke gold medallist's astonishing split of 56.78s helped them up into fourth.
Guy, who won his first gold earlier this week in the men's 4x200m freestyle relay, clocked exactly 50s in the butterfly to take Britain into the lead and Hopkin finished in 52s flat to spark exuberant celebrations.
Reflecting on a fourth swimming gold medal for GB, Hopkin said: "I was trying not to think about how far ahead we were of them 'cause it's just irrelevant when you're in the water.
"When I turned I saw I still had a good bit of water and I just went for it. It's just an amazing feeling. I'm so privileged to be in this team."
Peaty collected his second medal of the Games in the medley after successfully defending his 100m breaststroke title earlier this week.
He said: "It's amazing to be a part of this with these amazing women and Jimmy, and it's just incredible."
Guy, who had withdrawn from the individual butterfly event, added: "It was a very hard choice, training for so long to do my individual race and to be told the day before you had to pull out, I was really upset, I was crying again
obviously!
"But it has paid off. It was worth not doing the butterfly cos I don't think I'd have done that time. It's paid off."