Duncan Scott shocked both himself and the world to produce the second-fastest freestyle split ever to anchor Great Britain's 4x100m medley relay team to gold.
The British team of Adam Peaty, James Guy, Luke Greenbank and Scott set a European record to edge ahead of second-placed USA and Russia, who claimed bronze at the World Aquatics Championships in South Korea.
An incredible race saw 22-year-old Scott pick up the mantle on the last leg behind Russia, and almost a full second behind leaders USA.
But Scott wasn’t deterred and delivered a blistering anchor to haul in Russia, and subsequently USA’s Nathan Adrian, with a new European record of 3:28.10.
The Rio Olympian’s split of 46.14 is the second-fastest freestyle in history, with only USA’s Jason Lezak going faster with 46.06 at the 2008 Olympics.
“When you get to this level times well, they’re not irrelevant, but it just comes down to racing,” said Scott after picking up the gold medal.
“The boys put me in an incredible position and I just had to try and execute a good race plan. I can’t say I thought I had that split in me and I’m sort of speechless!”
The gold medal is Peaty’s third of the Championships and fourth overall after he defended his 50m and 100m breaststroke titles as well as taking bronze in the mixed 4x100m medley relay – while it takes the GB total to seven in Gwangju, with three golds.
Peaty commented: “This is incredible! I thought Jimmy (Guy) could hold his ground and as soon as Duncan dived in I thought ‘we’re going to get bronze’.
“With 25m to go I was jumping up and down like never before and the last 10 metres he just got his head down and took him out.
“For me, that’s better than Olympic gold and anything else, as when you do it as a team, and the fact the Americans have never been beaten in this event I don’t think, it’s just amazing.”
The men’s team had already secured a place at the Tokyo 2020 Olympic Games by virtue of finishing fourth to qualify for the final.
The women’s 4x100m medley team also successfully secured a place at Tokyo 2020 with the quartet of Georgia Davies, Molly Renshaw, Alys Thomas and Anna Hopkin finishing eighth in their final.
Hopkin closed out her Championships with seventh in the women’s 50m freestyle final while Max Litchfield also came seventh in the men’s 400m medley.