Doubell's first major international victory in 800 metres was at the World Student Games in Tokyo in 1967 in a time of 1:46.7. His next season (the Olympic season) was severely curtailed by Achilles' tendon injuries, and he was unable to compete for six months prior to the Olympic Games in Mexico City.[1] Doubell, however, was able to recover in time for Mexico City and won the 800 m gold medal, passing the pre-race favourite Wilson Kiprugut of Kenya down the straight to win in a world record equalling time of 1:44.3.[1]
Doubell had planned to compete at the 1972 Olympics in Munich, but was prevented from doing so by calf injuries, which brought on his retirement from competitive athletics.[2]
Post-athletic career
After retirement from sports, Doubell enrolled at Harvard Business School. He then worked as a Head of Relationship Management and a Director and Divisional Head of Corporate and Institutional Banking of the Deutsche Bank Group in Australia. He was a Director of Telstra Stadium in Sydney until 2007.[1]