During the 1939–1945 war he served on the staff of Lord Mountbatten at Combined Operations Headquarters, S.E.A.C. in the RAF; CO HQ, 1942–43; HQ SACSEA (Wing Comdr i/c Inter-Allied Records Section), 1943–46.
The Attack on the Iron Coast (film) depicts an account of Allied Combined Operations Headquarters commandos executing a daring raid on the German-occupied French coast during the Second World War.
Special Operations Executive | headquarters | Chief of Naval Operations | Nordic combined | Pacific Theater of Operations | Supreme Headquarters Allied Powers Europe | United Nations Headquarters | Headquarters | United States special operations forces | United States Special Operations Command | Operations management | Imperial General Headquarters | Headquarters Marine Corps | Business operations | Security Forces Headquarters - Jaffna | NASA Headquarters | Mediterranean Theater of Operations | Joint Special Operations Command | Combined Military Services Museum | Chief of Naval Operations Strategic Studies Group | 509th Operations Group | combined oral contraceptive pill | combined | Civil Operations and Revolutionary Development Support | Alpine skiing combined | Victoria Police Special Operations Group | United Nations headquarters | Security Forces Headquarters – Jaffna | Permanent Joint Headquarters | Nordic combined at the 1968 Winter Olympics |
During the Second World War he was a Major in the Intelligence Corps serving with the Combined Operations Headquarters and Special Air Service as a specialist in Air Photography.
During the planning stage, Durnford-Slater went to London where he worked out most of the details with David Niven, who was then serving as a staff officer in the Combined Operations Headquarters.