The Australian then refused to stand on the podium next to Sun at Gwangju, South Korea in 2019 after the Chinese swimmer won his fourth consecutive 400-meter freestyle world championship gold medal. Horton placed second, taking silver in a reversal of their Olympic final in 2016 when the Australian won gold.
Sun was banned from international swimming for four years, three months by the Court of Arbitration for Sport in 2021 for refusing to give a sample and tampering with a doping control.
Horton won a bronze medal as a prelim swimmer in the 4 x 200 meter freestyle at the Tokyo Games, after failing to qualify for the Australian team to defend his 400-meter gold from Rio.
He also won seven world championship medals, four Pan Pac Championship medals, and eight Commonwealth Games medals, including four gold.