American Michael Phelps has become the most successful Olympic athlete of all time by claiming the 10th and 11th gold medals of his amazing career. Phelps collected his fourth gold in the 200 metres butterfly and made it five out of five just under an hour later in the 4x200m freestyle relay - both in world record times.
Added to his six golds from Athens four years ago, the two victories saw Phelps surpass the nine golds won by Paavo Nurmi, Carl Lewis, Mark Spitz and Larysa Latynina to cement his place in Olympic history.
The 23-year-old led from the halfway point in the butterfly but was made to battle hard to win in a world record time of 1:52.03 seconds, beating his own previous best by 0.06s ahead of Hungary's Laszlo Cseh and Japan's Takeshi Matsuda.
"I couldn't see anything for the last 100m, my goggles pretty much filled up with water," said Phelps, who remains on target to surpass Spitz's achievement of seven golds in one Games.
"It just kept getting worse and worse through the race and I was having trouble seeing the walls to be honest. But it's fine. I wanted to break the record and wanted to go 1:51 or better but in the circumstances I guess it's not too bad."
As expected, Phelps then led off a dominant American quartet in the 4x200m relay, swimming the first leg more than two seconds under world record schedule.
His team-mates Ryan Lochte, Ricky Berens and Peter Vanderkaay carried on where he left off and eventually clocked a new world record time of 6:58.56, the first time the seven-minute barrier has been broken and almost five seconds quicker than their previous best.
Phelps returned to the water this afternoon to win heat six of the 200m individual medley and will be back at the pool tomorrow for heat nine of 100m butterfly.
World records were the order of the day as France's Alain Bernard and then Eamon Sullivan lowered the 100 metres freestyle best with the Australian in possession of the record following a time of 47.05secs in the second semi-final.
Another world record was broken in the women's 200m freestyle, Italian Federica Pellegrini taking gold in a time of 1:54.82 to lower her own mark set earlier in the week by 0.63s, before Australian Stephanie Rice lowered her own mark in the 200m individual medley to 2:08.45.