A boxing champion in the lightweight division during his service with the British army, Boustead was recruited to captain the British team in the modern pentathlon at the 1920 Summer Olympics. He finished joint 14th in a field of 23 competitors in his only Olympic appearance. He then continued his military career and, after transferring to the Gordon Highlanders, he was seconded from them to serve in Sudan beginning 19 November 1924. A seasoned explorer, he participated in both the 1926 British expedition to Kangchenjunga and the 1933 expedition to Mount Everest, organized his own mountaineering expedition in Sikkim, explored the Libyan desert with Ralph Alger Bagnold in 1932, and traversed the wastes of Greenland.