Michael Phelps won his 22nd Olympic gold medal with a dominant performance in the final of the 200m individual medley in Rio.
The American great powered clear on the freestyle leg to put the race to bed, coming home well clear of Japan's Kosuke Hagino and Shun Wang of China.
Phelps was challenged hard by Brazilian star Thiago Pereira and his old rival, and compatriot, Ryan Lochte over the first three lengths but neither man could live with him in the final 50m.
And both would pay for their early exertions as they dropped out of the medals completely, allowing Hagino to snatch what had seemed an unlikely silver.
Britain's Dan Wallace could never make an impact in the final and finished last as Phelps became the first swimmer to win the same event at four consecutive Games.
"This has been a very, very special week so far, for me, closing out my career," said Phelps.
"I'm enjoying the sport like I did when I was 18. My body definitely doesn't feel like an 18-year-old. Getting out of the pool may take a little bit more energy, it might be a bit harder, but it's just as sweet standing on top of the podium listening to your national anthem play.
"Hopefully I have the chance to do it again. That's something when I do retire I will miss.
"Whenever I hear the national anthem there are so many memories always going through my head and pretty much every time I hear it I'm in tears. I tried to hold it back today. It didn't work."
There was also disappointment for Britain's Chloe Tutton in the final of the 200m breaststroke as she was denied a bronze medal by six-hundredths of a second.
Tutton appeared set for third place in the closing stages of the race but she was touched out by China's Shi Jinglin - Japan's Rie Kaneto claimed gold.
The Briton also missed out on regaining the British record as she clocked two minutes 22.34, one-hundredth off the new mark set by Molly Renshaw on Wednesday. Renshaw finished sixth in the final.
Tutton admitted there was a tinge of disappointment, especially with silver going to convicted drug cheat Yulia Efimova of Russia.
She said: "Being in fourth place is a bit gutting, no matter who is in front of you. I would've preferred it to have been a completely clean Games.
"I couldn't help who was here. I'm not happy with it, but it's just the way it is. People just have to get on with it. I would've preferred to have a medal."
There was a British record to be celebrated on Thursday, though, as Ben Proud clocked a sensational 21.54 seconds to claim a place in the final of the men's 50m freestyle.
Proud led for much of his semi-final before being edged by Ukraine's Andriy Hovorov and Anthony Ervin of the United States, but he has the new record to look back on ahead of Friday's final.
And Katie Ledecky put herself in place for a fourth gold medal of the 2016 Games by breaking the Olympic record in the 800m freestyle heats.
United States star Ledecky clocked eight minutes 12.86 seconds in winning her race by nearly seven seconds with Britain's Jazz Carlin setting the third fastest qualifying time and putting herself in with a chance of a second medal.