Politician. He acceded to the Earldom of Fife on the death of his father, William Duff (c.1696 - 1763). He gave the town of Macduff, in the old country of Banff, its name, having changed it from Doune in 1783. He extended the town and built a harbour ensuring economic prosperity.
He died in London but is buried in the family mausoleum at Duff House.