As a conscientious objector, he could not serve in a combatant role, but was accepted into the Royal Air Force (RAF) Medical Services, as he had previously worked with the St John Ambulance Brigade. He served in the RAF in both England, and Asia (India and Burma, where he worked in intelligence, and was awarded the Burma Star). While there he undertook studies of Indo-Malayan and Sikkim-Himalayan tropical vegetation,[8] carried out botanical explorations, taught biology to troops and began work on his Botanical Latin.[lower-alpha 5] His wartime observations led to collaborative publications such as An enumeration of the flowering plants of Nepal (1978–1982),[41] Beautiful Indian Trees (2nd ed.