Ben Whittaker earned a silver medal but was out-foxed by the wily Cuban Arlen Lopez in the Olympic light-heavyweight final on Wednesday morning.
Whittaker's is the second silver medal for Team GB's boxers - Pat McCormack earned the same in the welterweight division - among a record six medals that will be brought home from Tokyo 2020.
But Whittaker's bid for GB's first boxing gold of the Games was thwarted by Lopez, who became a back-to-back Olympic champion after also winning at Rio 2016.
Lopez won a split decision to leave Whittaker's head in his hands.
Whittaker's nimble footwork and his speedy jab was impressive but the judges did not score the opening round in his favour.
Lopez was succeeding in closing the distance against the far taller and rangier Whittaker, who was being forced to miss too many punches.
An exciting exchange towards the end of the second saw both men land, but Whittaker's left hook was the most significant shot and clearly annoyed his Cuban rival.
Whittaker was unable to force the issue in the final round as the veteran Lopez controlled proceedings by switching between orthodox and southpaw.
As well as silver medals for Whittaker and McCormack, Frazer Clarke and Karriss Artingstall will take home bronze.
Galal Yafai at flyweight and Lauren Price at middleweight are set to compete in semi-final fights.