Michael Phelps became the first male swimmer to win the same event at three successive Olympics when he clinched the men's 200 metres individual medley gold medal at the London Games.
Phelps, who won the event at the Athens and Beijing Games, relegated compatriot and world champion Ryan Lochte to silver while Hungary's Laszlo Cseh took bronze.
The victory gave Phelps his 16th Olympic gold medal and 20th overall in his career.
Only two swimmers had ever won the same individual event at three Olympics, Australia's Dawn Fraser, in 100 freestyle in 1956, 1960 and 1964, and Hungary's Krisztina Egerszegi in 200 backstroke in 1988, 1992 and 1996.
It is a feat that had eluded generations of the best male swimmers until Phelps, who had the chance of doing it in four different events in London.
He came fourth in the 400 individual medley and looked to set to achieve the feat in his favoured 200 butterfly but was pipped by South Africa's Chad le Clos on the final stroke.
Phelps still has the 100 butterfly to come on his programme, with the American the second fastest qualifier into the semi-finals, which will take place later on tonight.
Earlier, Tyler Clary upset his American team mate Lochte to win the men's 200 metres backstroke gold medal at the London Olympics this evening.
Lochte led at all the turns but faded on the last lap as Clary drew level with him then got his hands on the wall first in a tight finish to win his first Olympic gold medal a time of one minute, 53.41 seconds.
Japan's Ryosuke Irie, runner-up to Lochte at last year's world championships, also made a late charge to grab the silver while Lochte won the bronze.
Lochte won the same event in Beijing four years ago and was attempting an extraordinary double today, trying to win the 200 backstroke and 200 individual medley within half an hour.
Rebecca Soni broke the world record for the second time in 24 hours to win the women's 200 metres breaststroke gold.
The American surged clear of her rivals after trailling after the first lap then taking the lead at the halfway stage to win in a time of two minutes, 19.59 seconds, slashing 0.41 off the previous record of 2:20.00 she set in Wednesday's semi-finals.
Japan's Satomi Suzuki won the silver medal and the bronze went to Iuliia Efimova of Russia.
Soni also won the four-lap event in Beijing four years ago and by winning in London she became the first woman to successfully defend a breaststroke title at the Olympics.
Ranomi Kromowidjojo of The Netherlands ensured there would not be an American clean sweep of the evening's four finals, powering to victory in the 100m freestyle and lowering her Olympic record - set yesterday - to 53.00.
The 21-year-old was only fourth at the turn but stormed down the final length to finish ahead of Aliaksandra Herasimenia and China's Yi Tang.