During World War II Broom-Lynne served as a warden with the Civil Defence Service in Westminster (1940–1945). It was at this time that he may have first exhibited his work to the general public. Both The West London Press and Chelsea News and The Hampstead News and Golders Green Gazette record artworks credited to Broom-Lynne in exhibitions of civil defence artists in 1941 and 1942 respectively.
