(Frederick) William (Dampier) Deakin was born 3 July 1913, the eldest son of Albert Witney Deakin of Aldbury, Tring, Hertfordshire. Deakin married Margaret Ogilvy, daughter of Sir Nicholas Beatson Bell in 1935 with whom he had two sons. The marriage was dissolved in 1940 and in 1943 Deakin married Livia Stela, daughter of Liviu Nasta Bucharest.

Deakin was educated at Westminster School, then at Christ Church, University of Oxford. He was a Fellow and Tutor at Wadham College, Oxford, 1936-49; Research Fellow, 1949; then Honorary Fellow, 1961. Deakin served in the Second World War of 1939-45 with the Queen’s Own Oxfordshire Hussars, 1939-41, and was seconded to Special Operations, War Office, 1941. He led the first British Military Mission to Tito in May 1943 and was First Secretary at the British Embassy in Belgrade from 1945-46.

In addition to these positions, Deakin was a Literary Assistant to Sir Winston Churchill from 1936-1940 and also from 1945-55 and is described by Churchill's biographer, Sir Martin Gilbert, as being "at the centre of the web of all Churchill's literary efforts." From 1936 onwards, Deakin was a literary assistant to Churchill on his biography of his famous ancestor, John, 1st Duke of Marlborough (which Churchill wrote between 1929-38).

He died at his home in the south of France on 22 January 2005.

His publications include: "The Brutal Friendship" (1962) and "The Embattled Mountain" (1971).