Tom Dean powered to the gold medal in the men's 200m freestyle at the Tokyo Olympics on Tuesday, heading a British one-two with Duncan Scott taking silver, breaking a 113-year record.
It is the first time since 1908 that two male British swimmers have finished on the Olympic podium together.
Dean won in a time of 1:44.22 with Scott just 0.04 seconds behind him.
Team GB have won 13 medals so far in Japan, which is the best start for a British team in Games history. Britain have also claimed the highest number of gold medals for this point of the competition.
South Korea's Hwang Sun-woo was under the world record time at the 100m mark but faded badly to finish seventh as the British pair powered towards a spectacular finish.
The 21-year-old's gold was Britain's second in the Tokyo pool after Adam Peaty's success in the 100m breaststroke on Monday.
"I knew it was going to be a dogfight," Dean said. "I didn't know how people were going to swim it. I just race the race, and that's how it is."
Scott was narrowly above Dean in the rankings going into the Games and qualified fastest, but he was delighted for his teammate.
"Just a massive credit to Tom Dean," Scott said. "That was unbelievable. Olympic champion.
"To come along so far in the last 18 months, it's a pleasure to watch him. It's great to be able to say he's a good mate out of the pool."
In January, Dean caught COVID-19 for the second time in four months, putting him out of the pool for just less than seven weeks before his Olympic trials.
"The Olympic gold was a million miles away," Dean added. "It's amazing. It's a dream come true having a gold around my neck."
Huge garden party celebrations as Dean wins gold
GB swimmer Tom Dean's friends and family celebrate as he wins Olympic gold at Tokyo 2020.
Elsewhere on Tuesday, Team GB won a surprise bronze medal in the women's gymnastics team final for the first time since 1928.
The team were in seventh place after two pieces of apparatus but strong performances on the uneven bars from Amelie Morgan, Jessica Gadirova, Jennifer Gadirova and Alice Kinsella saw Britain claim third place.
The Russian Olympic Committee took gold ahead of USA. Simone Biles retired from the competition after just one piece of apparatus with a medical issue.
Team GB won bronze in the team dressage final with a score of 7723.0.
The team were second in the standings following the first two groups after strong runs by Carl Hester on En Vogue and Charlotte Fry on Everdale. But, the USA were not far behind.
Despite a valiant effort by Charlotte Dujardin on Gio to score 2617.0, Team GB slipped behind the Americans in the final group and had to settle for bronze.
However, the medal secured Dujardin's place in history as she became the joint-most decorated British Olympian with five medals alongside Dame Katherine Grainger and tennis player Kathleen McKane Godfree.
The British trio will all be going for individual medals on Wednesday in the Grand Prix Freestyle.
In the triathlon, Georgia Taylor-Brown took silver despite suffering a flat tyre in the final lap of the 40 kilometre bike ride.
She rallied back and secured second place just 12 weeks after she was on crutches with a leg injury. The 27-year-old recovered in time and took silver to make it two second-place finishes for Great Britain in the triathlon after Alex Yee finished second in the men's on Monday.
Taylor-Brown had not raced since September but she managed to put together a remarkable performance in a triathlon which saw the start delayed due to the inclement weather in Tokyo.
"I got a stress response in my femur 12 weeks ago. My training had gone so well before then though, so that was a bit of a shock, but I knew I had all of that training in the bag," she said.
"I wanted to keep it private, you don't want to show your competitors your weaknesses, so I did just say I was ill. I've had six weeks of building my running back again. It's not perfect, it's not what I wanted or what anyone would want. I got myself into a really good position and I was as fit as I could have been on the start line today.
"About a week before we flew out I had to prove I was fit to compete, which was probably more stressful than today because it could have been taken away from me. But I proved I was fit, ready to go and did more than they asked me to do. I had to go in to today relaxed and that I'd done everything I possibly could, and I left everything out there."
She finished second behind Bermuda's Flora Duffy -- the island territory's first-ever Olympic gold medal.
"I planned for hot weather and for a slower race, which favoured me because of the lack of running I'd done recently," Taylor-Brown added. "I didn't have the speed that Flora had today, and I'm more than happy with silver. Without the injury I think I could have hung in there and maybe given her a bit more of a race. I think I've handled it very well and I'm proud to have got on the start line."
Bianca Walkden claimed her second Olympic bronze in the women's +67kg taekwondo, beating Poland's Aleksandra Kowalczuk 7-3.
The Briton held a narrow lead throughout the opening rounds, finishing the second 4-3 up. However, a trunk kick in the third round extended her lead and secured her the podium place.
Walkden, who also settled for bronze at Rio 2016, had earlier been denied a place in the final after a disappointing semifinal defeat to Lee Dabin, with the Korean producing a winning head kick in the last three seconds of the final round.
"I'm glad I came away with an Olympic medal but it was not the colour I trained for or expected," Walkden said.
"I gave my heart and soul in that semi and was a little bit unlucky with some of the decisions.
"I feel a little bit dead inside and it's killing me. It's a medal just not the colour I wanted, I might paint it over when I get it home, no-one has to know."
In the men's rugby sevens, Great Britain made a stunning comeback in their quarterfinal against USA, winning 26-21.
Team GB trailed by 21 points before a USA yellow card allowed them to take advantage and score three tries in the final seven minutes.
Earlier in the day, Britain fell short against defending champions Fiji in their final pool match, losing 33-7. Britain will face New Zealand in the semifinal.
Team GB's women's football team ensured their qualification through to the knockout stages after they came from behind to draw 1-1 against Canada. Coach Hege Riise's side topped Group E and will face Australia in the next round.
Great Britain's men fell 5-1 to Germany in their Pool B hockey match. Phil Roper opened the scoring, but Britain slumped to a heavy defeat. Despite the one-sided loss, captain Adam Dixon was adamant this will not be a hammerblow to their hopes of a medal.
"We can't take that game in isolation because we've had a positive start. This is a hiccup so to speak. It hurts a little bit more the fact that it's Germany," Dixon said.
"But we've got to pick ourselves up now because we've got two big games against the Dutch and the Belgians. Let's try to finish this pool stage off in a strong position. But yeah, we're kicking ourselves after that result today but we've got to turn it around in 48 hours' time."
Boxers Caroline Dubois and Pat McCormack both progressed through their first round of fights on Tuesday.
McCormack beat Sasha Radzionau from Belarus in the men's welterweight while Dubois beat Donjeta Sadiku in the women's lightweight.
Dubois was in control for the entirety of her fight apart from a brief moment of concern in the third round.
Her next competition is American Rashida Ellis in the last-16. No. 1 seed McCormack will face Uzbekistan's Usman Baturov in the quarterfinals.
Meanwhile, Cheavon Clark was knocked out of the men's heavyweight competition by Brazil's Abner Teixeira.
Andy Murray and Joe Salisbury beat Kevin Krawietz and Tim Putz 6-2, 7-6 (7-2) in the second round of the men's tennis doubles.
The pair sailed through the first set but were forced into a tiebreak in the second as Krawietz and Putz looked like they might force the match to a third set.
However, the British duo managed to pull the win back from the brink.
Murray is trying to become the first man to win four Olympic medals in tennis since it was brought back to the Games in 1988, focusing on the doubles competition after withdrawing from the singles competition with a minor thigh strain on Sunday.
"When we spoke about playing, I told Joe that if I had any physical issues I'd prioritise doubles over singles and that's why I made the decision," Murray said.
"I'd have been annoyed with myself if I'd decided to play with the issue, made it worse, lost my singles and not been able to perform well in the doubles.
"Physically it'll be OK for the rest of the tournament, but I will need to take a break afterwards."
Elsewhere in the tennis, Liam Broady knocked out Wimbledon semifinalist Hubert Hurkacz to reach the third round of the men's singles tournament.
He will face France's Jeremy Chardy in the last 16.
However, there were mixed results for Team GB in the badminton. Toby Penty and Kirsty Gilmour were both victorious in the first round of the men's and women's singles tournament but Chloe Birch and Lauren Smith in the women's doubles and Ben Lane and Sean Vendy in the men's doubles were eliminated.
Meanwhile, Britain's Sarah Davies came fifth in the women's 64kg weightlifting, finishing 9kg off the winner with a total of 227kg.
Elsewhere in weightlifting, Zoe Smith finished eighth in the 59kg competition with a total of 200kg. China's Kuo Hsing-chun took gold with an Olympic record 236kg.
There was heartbreak too for Kimberley Woods in the women's slalom K-1 after she picked up a 56-second penalty and finished 10th overall.
Tom Hamilton and Reuters contributed information to this report.