China's defending world and Olympic champion Zou Shiming won the men's light flyweight (46-49kg) gold on Saturday with a 13-10 win over Thailand's Kaeo Pongprayoon.
Zou, 31, defended the title he won in Beijing four years ago, but it was an unpopular decision with the crowd at London's ExCel Arena, who jeered the final score while Kaeo wept openly in the ring.
Zou is the first boxer to defend the light flyweight title and is the first Chinese to win two boxing gold medals.
He is also the first man to win three medals in the light flyweight having taken bronze at Athens 2004 and is the oldest Olympic champion at that weight.
"I'm very excited, but very tired as well," said Zou.
"Boxing in the Olympics starts on the first day and finishes right at the end, so it's very tiring.
"When I saw other people winning gold medals and watching their national flags being raised, I was envious. I couldn't wait to get this medal.
"It was an unbiased judges' decision. The judge gave me the result, so I won, but it's nothing to do with me."
Kaeo was disappointed not to have not scored more points in the first round.
"I thought that I'd won and I could see that the crowd thought I'd won as well," said the 32-year-old with tears in his eyes.
"Especially in the last round, I don't know why they deducted the points from me. I felt that it was my match.
"I'm still really happy that I got this silver medal.
"It might not be gold, but it's still silver, and I'm really proud that I can bring it back for the Thai people and everyone back in Thailand."
Having lost in the semi-finals, Ireland's Paddy Barnes and Russia's David Ayrapetyan won bronze medals.
Having won the world crown last year in Baku, Zou adopted a conservative approach in the final and frustrated his Thai opponent, taking the first round 2-1 and amidst plenty of holding winning the second 4-3.
Kaeo, 32, upped his work-rate in the third, landing a succession of shots to the body and Zou earned a warning for a rugby-style tackle on the Thai which saw both of them tumble to the canvas.
With both fighters getting frustrated, Kaeo was also warned, but Zou held on to win the third round 7-6 to retain his Olympic crown.