The son of the second duke (d. 1817), he was educated at Eton and St John's College, Cambridge, and before succeeding to the title was a Tory MP for Buckingham (1806), Westminster (1806), Launceston (1806-07), and Northumberland (1807-12). He was lord-lieutenant of Ireland (1829-30).

REFERENCES TO Hugh Percy, third duke of Northumberland:

Lord Henry Petty to Thomas Creevey, 28 January 1806 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Samuel Whitbread to Thomas Creevey, 10 November 1809 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Sydney Smith to Lady Grey, 22 November 1817 in A Memoir of the Reverend Sydney Smith. By his Daughter, Lady Holland. With a Selection from his Letters, edited by Mrs. Austin 2 vols (London: Longman, Brown, Green, and Longmans, 1855)

John Whishaw to Thomas Smith, 11 December 1819 in The “Pope” of Holland House: Selections from the Correspondence of John Whishaw and his Friends 1813-1840 (London: T. Fisher Unwin, 1906)

Thomas Creevey to Elizabeth Ord, 23 January 1820 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Thomas Creevey to Elizabeth Ord, 6 November 1820 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Thomas Creevey to Elizabeth Ord, 6 October 1827 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Thomas Creevey to Elizabeth Ord, 26 March 1828 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Thomas Creevey to Elizabeth Ord, 1 October 1828 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)

Lord Anglesea to Lady Morgan, 28 February 1829 in Lady Morgan’s Memoirs: Autobiography, Diaries and Correspondence. Second Edition, Revised 2 vols (London: Wm. H. Allen & Co., 1863)

Countess of Charleville to Lady Morgan, [April? 1830] in Lady Morgan’s Memoirs: Autobiography, Diaries and Correspondence. Second Edition, Revised 2 vols (London: Wm. H. Allen & Co., 1863)