A nephew of Esther Bensusan, the wife of Lucien Pissarro, and the son of Jewish socialist Ruth Bensusan-Butt (1877–1957), the first woman doctor to work in Essex, Bensusan-Butt was educated with his older brother John at Gresham's School, Holt, and then at King's College, Cambridge, where he was a student of John Maynard Keynes and indexed Keynes's magnum opus, the General Theory of Employment, Interest and Money.
Early in the Second World War he became private secretary to Frederick Lindemann, 1st Viscount Cherwell, then worked for Winston Churchill.
In September 1944, Bensusan-Butt was commissioned as a Temporary Sub-Lieutenant into the Royal Naval Volunteer Reserve,[4] serving on the minelayer HMS Cyclone.
[5] From 1949 to 1950 he was seconded to the Australian Prime Minister's Department, and he spent two periods of one year at Nuffield College, Oxford as a research fellow, in 1953–1954 and 1958–1959.
In 1962, he became a professorial fellow in the Research School of Pacific and Asian Studies (RSPAS) of the Australian National University, remaining there for fifteen years.