Adam Peaty revealed helping Great Britain men's 4x100m medley relay team beat America on the way to their maiden world title ranked alongside even his own Olympic gold medal success.
After successfully defending his 50m and 100m breaststroke titles in Gwangju, South Korea, Peaty claimed his third gold - and fourth medal of the Championships - on the final day of action in the pool on Sunday.
But the performance was far from being about just the Olympic 100m breaststroke champion as teammates Luke Greenbank, James Guy and especially Duncan Scott all contributed to a thrilling victory, setting a new European record time of three minutes, 28.10 seconds to edge out America and Russia.
After a solid backstroke leg from 200m backstroke bronze medallist Greenbank, Peaty took over and unsurprisingly got Britain in front at the next change, but Guy was passed on the butterfly leg by America's Caeleb Dressel and Russia's Andrei Minakov.
Scott still trailed at the final turn by 0.84 seconds but produced a strong finish to snatch victory, and his split of 46.14 seconds would have broken the world record in a regular 100m freestyle.
Described by former British world champion Karen Pickering as "one of the greatest relay swims I have ever seen", defeat for America was only the second time, disqualification aside, that they had lost the world relay event, having taken silver to Australia back in 1998. They are also unbeaten at Olympic level.
"This is incredible!" said Peaty, who also won bronze in the 4x100m mixed relay. "I thought Jimmy 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 10m 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."
For the British team, gold upgraded on the world silver won two years ago in Budapest while for Scott, who recorded the second fastest freestyle relay split of all time after American Jason Lezak's 46.06 in the 4x100m freestyle relay at the 2008 Olympics, it also added to the 200m freestyle bronze from earlier this week.
Afterwards he said: "When you get to this level times well, they’re not irrelevant, but it just comes down to racing. 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."
In the women's race, the British quartet of Georgia Davies, Molly Renshaw, Alys Thomas and Freya Anderson could only finish eighth as the United States took gold in a new world record time of three minutes and 50.30 seconds.
America topped the overall medal table with 13 golds ahead of next year's Olympics, while GB finished seventh with three golds, one silver and three bronze.