He was the son of the noted naval commander Admiral Adam Duncan,[1] Baron of Lundie who was Commander-in-Chief of the North Sea from 1795 to 1801 and defeated a Franco-Dutch fleet at the Battle of Camperdown in October 1797.

Later the same month he was honoured when he was raised to the Peerage of Great Britain as Baron Duncan, of Lundie in the Shire of Perth, and Viscount Duncan, of Camperdown and of Lundie in Our Shire of Perth.

[2] He was a Liberal politician and held minor office under Lord Palmerston from 1855 to 1858.

Lord Camperdown assumed the additional surname of Haldane, which was the maiden name of his paternal grandmother.

He was also a Liberal politician and served under William Ewart Gladstone as a Lord of the Admiralty from 1870 to 1874.