He was born in Edinburgh the son of the personnel officer to the LNER railway. His early life was unsettled due to his father’s frequent job-related relocations. He eventually settled and his first fixed school was Edinburgh High School. A neighbour, Mary Noble FRSE, a plant pathologist, encouraged an interest in plants and agriculture, and on this basis he entered Edinburgh University in 1944. However, he was called up to serve (in the Fleet Air Arm) soon thereafter and was not demobbed until 1947. On his return to Edinburgh University he instead decided to study Geology (under Prof Arthur Holmes), graduating BSc in 1951. Holmes encouraged him to undertake a PhD, beginning by remapping Ben Hiant near Ardnamurchan. However it was hard to surpass the original survey work by James Ernest Richey FRSE and Duff abandoned the project. He did however, fall in love with Ardnamurchan and bought a house there.
After his doctorate, he immediately obtained a post mapping with the British Geological Survey being tasked with mapping the coalfields of Nottinghamshire and Derbyshire.
In 1954 he was offered a post as Lecturer in Economic Geology at Edinburgh University. He rose to Senior Lecturer and Associate Dean of the Faculty of Science. In 1965 he took a sabbatical to research the coalfields of New South Wales in Australia for the University of Sydney. He left Edinburgh University in 1974 to take a post as Professor of Applied Geology at Strathclyde University. In Strathclyde he was also Dean of the School of Civil Engineering. In 1982 he left academia to take on a critical job as Chief Coal Review Geologist to British Petroleum (BP).
In the period 1974 to 1982 he used his summer vacations as a consulting geologist in British Columbia. This required worldwide travel in search of fuel supplies.
He had several health issues including having a disc removed in 1946 which ended his sporting life. He had a sextuple heart bypass in 1985 and retired in 1987. He died of cancer in Edinburgh on 23 March 1998.
Duff was editor of the Geological Journal and also contributed to the Scottish Journal of Geology and Applied Earth Science. Other works include:
- Cyclic Sedimentation (1967) with E K Walton
- Geology of the Lothians and South East Scotland (1976)
- Geology of England and Wales (1992)
He was married to Jean in 1952 and had three children, Peter, Alistair and Jennifer.
- Proceedings of the Royal Society of Edinburgh: obituaries 1998
- Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002 (PDF). The Royal Society of Edinburgh. July 2006. ISBN 0 902 198 84 X.