 There he won the silver medal in the 100-metre butterfly, and bronze in the 4×100-metre medley relay, alongside Erik Fish, William Mahony and Robert Kasting.A specialist in the butterfly stroke, his greatest achievement was winning the 100-metre butterfly race at the 1973 World Aquatics Championships in Belgrade – the first world championship swimming performance by a Canadian in over 60 years.Robertson also swam on the third place 4×1000-metre medley relay team there.