Sir Antony Duff (1920–2000) joined the Service as its Director General in 1985. He previously had distinguished military and diplomatic careers.
During the Second World War, he served as a submariner and commanded HMS Stubborn. He earned a Distinguished Service Order for a daring escape from German destroyers in February 1944. Due to eye injuries suffered during this action, he left the Royal Navy and joined the diplomatic service after the war.
He served in a variety of high-profile diplomatic roles including ambassador to Nepal, high commissioner to Kenya and head of the Foreign and Commonwealth Office's Africa department. He played a key role in the independence negotiations for Southern Rhodesia (now Zimbabwe). He served as the country's last Deputy Governor before its independence in 1980. He was knighted in the same year.
Sir Antony subsequently became Deputy Secretary at the Cabinet Office, serving as Intelligence Coordinator, and chaired the Joint Intelligence Committee. He became Director General of the Security Service in March 1985. He served for two and a half years before retiring in January 1988. Under his management, he carried out important reforms of the Service to establish new working practices and personnel arrangements. This increased the Service's ability to deal with the terrorist threat.