‘Bill’ Wager, after undergraduate and postgraduate studies at the University of Cambridge, became a lecturer at the University of Reading in southern England in 1929. He was granted leave in the 1930s to participate in lengthy expeditions that explored the geology of Greenland, an island largely within the Arctic Circle. With friends made on those expeditions, he became in June 1940 an early recruit to the Photographic Development Unit of the Royal Air Force that pioneered the development of aerial photographic interpretation for British armed forces. He was quickly appointed to lead a ‘shift’ of interpreters. The unit moved in 1941 from Wembley in London to Danesfield House in Buckinghamshire, known as Royal Air Force Medmenham, to become the Central Interpretation Unit for Allied forces—a ‘secret’ military intelligence unit that contributed significantly to Allied victory in World War II. There Wager led one of three ‘shifts’ that carried out the ‘Second Phase’ studies in a three-phase programme of interpretation that became a standard operating procedure. Promoted in 1941 to the rank of squadron leader in the Royal Air Force Volunteer Reserve, he was given command of all ‘Second Phase’ work. Sent with a detachment of photographic interpreters to the Soviet Union in 1942, he was officially ‘mentioned in a Despatch’ on return to England. By the end of 1943 the Central Interpretation Unit had developed into a large organization with an experienced staff, so Wager was allowed to leave Medmenham in order to become Professor of Geology in the University of Durham. He resigned his commission in July 1944. Appointed Professor of Geology in the University of Oxford in 1950, he died prematurely from a heart attack in 1965, best remembered for his work on the igneous rocks of the Skaergaard intrusion in Greenland and an attempt to climb Mount Everest in 1933.