Duncan Armstrong won Olympic Gold at the 1988 Seoul Games in the 200m freestyle breaking the world record.

Duncan arrived in Seoul for the 1988 Summer Olympics ranked 46th in the world, facing a trio of past and current world record holders in the men’s 200-metre freestyle: Matt Biondi of the United States, Artur Wojdat of Poland, and Michael Gross of West Germany. Although not favoured to win, Duncan had developed a strong sense of confidence after years of 20 km per day of training. “You look down your lane and know you’ve done everything you possibly can, and you’re prepared for this race. Someone has got to win it. Why not me?” As a back-end swimmer, master coach Laurie Lawrence planned for Duncan to swim as close to Biondi’s adjacent lane as possible, with Duncan effectively drafting or surfing the American’s wake. At 150 metres, Duncan was in third place, but he surged past Sweden’s Anders Holmertz and then Biondi in the final 25 metres to claim the gold medal with a new world-record time.

Later, in the men’s 400-metre freestyle, Duncan was once again slow out of the blocks, turning last at the 100-metre mark, and still being second-to-last at the 300-metre mark. However, he finished strong, and in a photo finish, claimed the silver medal behind East German Uwe Dassler’s new world-record time. He had cut more than five seconds off his previous personal best; all three medallists—Dassler, Duncan and Artur Wodjat—broke the previous 400-metre freestyle world record. Duncan was also a member of the Australian team that finished fourth in the men’s 4 x 200m freestyle relay. For his Olympic successes, he was awarded the Young Australian of the Year Award for 1988.