Background
Duncan was born in Watervale, South Australia, the second son of John Duncan, a wealthy and influential pastoralist and politician, and his wife Jean, née Grant.
Duncan was born in Watervale, South Australia, the second son of John Duncan, a wealthy and influential pastoralist and politician, and his wife Jean, née Grant.
He was educated at Street Peter"s College, where he did not shine academically, but excelled at cricket.
He was elected to the South Australian Legislative Council for the Liberal Party by the Midland electorate in March 1918 and was re-elected in 1924, 1930, 1938, 1944, 1950 and 1956, finally retiring in 1962. He was elected President of the South Australian Legislative Council in 1944 and held the position until 1962.
He was a longtime member of the Royal Agricultural and Horticultural Society, and its president in 1924 and 1925.