Son of the Hon. Alexander Duff, who succeeded his brother as the 3rd Earl of Fife in 1809, the sitter was educated in Edinburgh and married Mary Caroline, second daughter of John Manners, in 1799. He volunteered to join the Spanish patriotic army in the war against Napoleon in 1808, perhaps partly to distract himself following the death of his wife in 1805. He attained the rank of Major-General and served with great distinction in the Peninsular campaigns particularly at the Battle of Talavera, in which he was severely wounded, but also in the defence of Cadiz and later in the attack on Fort Matagorda. In 1811 he succeeded as the 4th Earl of Fife and returned to England. He was elected Member of Parliament for Banffshire in 1818 and was created a Peer of the United Kingdom, as Lord Fife, and made a Knight of the Thistle in 1827. In later life he retired altogether to Scotland where he lived at Duff House, Banffshire. He was succeeded by his nephew James Duff.
This portrait is an autograph version of the full-length portrait which the artist exhibited at the Royal Academy in 1815, the year that he was elected a member of the Royal Academy (for which see D. Mackie, op.cit., no. 231).