 During the first part of the First World War Redmayne served as head of the Production Department of the Control of Coal Mines.From 1917 to 1919 he was the chief technical advisor to the Controller of Coal Mines and in 1919 acted as an assessor to Sir John Sankey who was the chairman of the Royal Commission on Coalmines.From 1918 he was also the chairman of the Imperial Mineral Resources Bureau, resigning as chief inspector in 1919 to dedicate more time to the bureau and to set up a private engineering consultancy.