Michael Phelps became the most decorated Olympian of all time, the US 4x200m freestyle relay gold giving him a 19th medal after bittersweet silver in the 200m butterfly.
Phelps' record of 15 Olympic gold medals includes eight from his spectacular Beijing Games campaign as well as six from Athens in 2004. He also won two bronze in Athens and has won two silver in London.
South Africa's Chad le Clos denied Phelps' bid for a 200m butterfly treble by a hair yesterday, but silver allowed the US superstar the consolation of matching Soviet gymnast Larisa Latynina's record of 18 Olympic medals.
Phelps returned an hour later and teamed with Ryan Lochte, Conor Dwyer and Ricky Berens to capture the 4x200m free relay gold ahead of France and China.
For most of the race, it looked like Phelps would make his 18th career medal gold.
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But Le Clos, third at the final turn but clinging stubbornly to Phelps and Takeshi Matsuda, relentlessly pressed his challenge and plunged past Phelps at the finish to win in 1min 52.96sec.
Phelps, who had led at every turn in a quest to become the first man to win the same Olympic swimming event at three successive Games, was just five-hundredths of a second back in 1:53.01 and Matsuda settled for bronze in 1:53.21.
Le Clos, 20, thrust his body out of the water in delight upon seeing the scoreboard. Then he perched on a lane rope with his head in his hands as he tried to absorb his achievement in his first Olympics.