Educated at Dover College, Walmsley was commissioned into the Loyal North Lancashire Regiment in January 1916 during the First World War.Air of Authority – A History of RAF Organisation – Air Marshal Sir Hugh Walmsley He was seconded to the Royal Flying Corps later that year and received a permanent commission in the Royal Air Force in 1919. He was appointed Officer Commanding No. 33 Squadron in 1933 and Officer Commanding No. 8 Squadron in 1935 before becoming Station Commander at RAF Abingdon in 1937.
