Sun Yang came within a whisker of breaking the world record to win the men's 400 metres freestyle final at the London Aquatics Centre on Saturday and became the first Chinese man to win an Olympic swimming title.
The 20-year-old sprinted clear of his rivals on the final 100 metres to win the gold in three minutes 40.14 seconds, just 0.07 outside the world record of 3:40.07, set by Germany's Paul Biedermann at the 2009 world championships in Rome during the height of the bodysuit controversy.
South Korea's Park Tae-hwan, who won the event in Beijing four years ago, finished second after winning an appeal just to compete in the final.
He led for the first 300 metres under world record pace and held on for second in 3:42.06. American Peter Vanderkaay was third in 3:44.69.
The 22-year-old Park easily won his morning heat only to be told he had been disqualified for a false start but the Korean Swimming Federation protested to the sport's world governing body and succeeded in getting the decision overturned.
Sun also holds the world record for the 1500 freestyle, the longest event in the pool, which he set at last year's world championships in Shanghai and is an overwhelming favourite to win the gold in London.
Biedermann failed to qualify for the final after finishing 13th overall in the heats.