China's Zou Shiming became the first man to retain the light-flyweight Olympic title but only after claiming a controversial victory in the gold medal match against Thailand's Kaeo Pongprayoon.
Zou, who defeated Ireland’s Paddy Barnes on countback in the semi-final, followed up his success in Beijing four years ago with a 13-10 win over Pongprayoon.
However, the decision was greeted by a chorus of boos at ExCeL after a bout where Pongprayoon seemed to have the better of at least two of the three rounds.
Zou, the top seed and world champion, was nevertheless awarded all three rounds.
A warning in the third round for negative tactics and holding appeared to give Pongprayoon a chance of victory but just moments later he was given the same penalty.
It seemed a harsh decision but it ultimately decided the result.
The neutrals in ExCeL made their feelings known when the verdict was handed down, loudly booing Zou and cheering Pongprayoon as his arm was raised by his trainer.
"I feel that I won and I could see that the crowd thought I won," said the Thai.
"I don't know why I lost. I think the points system in the Olympics is wrong or strange - not just my fight but others didn't go the way they should have."
Ukrainian top seed Oleksandr Usyk claimed the prestigious heavyweight gold after seeing off the committed Italian Clemente Russo.
It was a contest befitting the stage, Usyk the reigning world champion taking on the silver medallist from Beijing.
Second seed Russo landed a right hand for the first score of the fight and, perhaps surprisingly, moved into a 3-1 lead after one round as Usyk had a sluggish beginning.
Things changed in the second, Usyk initially appearing to land a knockdown with a left hook only for the referee to rule that Russo had stumbled.
There was a big exchange of blows as the second came to an end but Usyk had the better of it and took the round 7-5.
He closed out a 14-11 victory in the final round as Russo, looking to force the win, missed with a series of big hooks only to be caught by his more measured rival on more than one occasion.
Usyk then celebrated victory with a dance in the middle of the ring, while Russo appeared content with his second successive Olympic silver.
Usyk's compatriot Denys Berinchyk had earlier performed a similar mid-ring routine, but only after losing his light-welterweight gold medal match to classy Cuban Roniel Iglesias.
The judges awarded the bout to Iglesias by a handsome score of 22-15, but it did not flatter the 23-year-old - who had lost to the same opponent in last year's World Championships.
Berinchyk went on to take silver in Baku and had to settle for the same here as Iglesias - the bronze medallist in Beijing four years ago - made 11 scoring shots in a one-sided final round that saw the Ukrainian's defence fall to pieces.
Iglesias had done enough to edge the first two rounds by a point apiece but in the closing stages the reigning Pan-American champion kept connecting, most obviously with a thunderous left-hand counter, to win in style.
Celebrating his podium-topping performance, Iglesias said: "Today is the day which is most important in my career. Without my family I could not achieve this and they will be so proud. I dedicate this to them."
Japanese middleweight Ryota Murata was the remaining gold medallist of an action-packed night, edging a close final against lively Brazilian fighter Esquiva Falcao Florentino 14-13.
Murata was seeded second in the draw, with Florentino fourth and the bout was as close as may have been expected from two of the medal favourites.
The pair have previous form, with Murata victorious in the semi-finals of the World Championships last year - a competition where he went on to claim silver while condemning Florentino to bronze.
Murata was at his most active in the opening minutes, using his reach to penetrate and move into a 5-3 lead.
Florentino, so impressive in his win over Anthony Ogogo yesterday, responded impressively, dictating the tone in the second round with a consistent flurry of right jabs.
Murata was put on the back foot but his defence held firm and he remained 9-8 in front going into the final round.
Again, Florentino went on the attack and briefly forced his opponent into a dangerous position on the ropes before losing his footing.
Florentino made all the running but Murata was deflecting enough shots to draw the round and take the Olympic title.