Politician. Member of Parliament for Banff, Duff was created the 1st Earl of Fife and Viscount MacDuff in 1759 (the original MacDuff line of Earls of Fife having expired in 1353).
Duff commissioned William Adam (1689 - 1748) to build Duff House, but having quarrelled with the architect, never lived in the house. He died in Rothiemay, near Huntly, but is buried in the family mausoleum at Duff House.