Background
Duff was the eldest illegitimate son of James Duff, 2nd Earl Fife (1729–1809), and Margaret Adam, of Keith. As his mother was of humble status, her three children with Fife were placed in the guardianship of William Rose Fife"s factor.
Duff was the eldest illegitimate son of James Duff, 2nd Earl Fife (1729–1809), and Margaret Adam, of Keith. As his mother was of humble status, her three children with Fife were placed in the guardianship of William Rose Fife"s factor.
Fife liked Duff and took good care of him, sending him to Keith Academy and at King"s College, Aberdeen, where he graduated Master of Arts in 1771, and after he entered the army paid for Duff"s promotions.
Duff entered the army as an ensign in the 1st Foot Guards on 18 April 1769. James Duff was promoted captain and lieutenant-colonel, on 18 July 1780, colonel on 18 November 1790. His regiment was part of the expeditionary force sent to Flanders to campaign against the French as part of the First Coalition (the British contingent under the command of Prince Frederick, Duke of York).
He fought at the Battle of Valenciennes commanding the guards" light infantry battalion in 1794.
On 30 October he was promoted to major-general. In 1797, Duff received the command of the Limerick district.
While there he rendered important services during the Irish Rebellion of 1798, and managed to keep his district quiet in spite of the state of affairs elsewhere. His name is associated with the Gibbet Rath executions.
He was elected Member of Parliament for Banffshire (1784-1789), and colonel of the 50th foot from 1798 to death.
Duff was promoted lieutenant-general on 1 January 1801, and general on 25 October 1809, and at the time of his death, at Funtington, near Chichester, on 5 December 1839, he was the most senior general in the British army, and was one of the few officers who held a commission for over seventy years. He had as aides-de-camp during his Limerick command two famous officers, William Napier and James Dawes Douglas. There are numerous allusions to him in the of Sir William Napier.
Duff benefited from the compensation paid out following the abolition of slavery in 1833.
He received a payment of £4,101,0s,1d, an approximate £347,000 in 2015, made by the government of United Kingdom as recorded by the Slave Compensation Commission and the records held at the National Archives in London. On 12 August 1785 Duff married Basilia (d 1849), daughter and heir of James Dawes of Rockspring, Jamaica, through whom he gained control of a considerable fortune.