Dictionary of National Biography, 1885-1900/Trevor, John Hampden-
TREVOR, JOHN HAMPDEN-, third Viscount Hampden (1749–1824), diplomatist, was the second son of Robert HampdenTrevor, first viscount Hampden and fourth baron Trevor [q. v.], by his wife Constantia, daughter of Peter Anthony de Huybert, lord of Van Kruyningen in Holland. He was born on 24 Feb. 1748–9 in London, and baptised on 26 March at St. George's, Hanover Square.
Hampden-Trevor was educated at Westminster school, and matriculated from Christ Church, Oxford, 28 Jan. 1767. He graduated B.A. 20 Oct. 1770, and was created M.A. 9 July 1773. Following his father's career, he was appointed, 8 April 1780, minister-plenipotentiary at Munich to the elector palatine, and minister to the diet at Ratisbon. By the instructions given him, 28 April 1780, by Lord Stormont, he was ordered to be particularly watchful with regard to any treaty of subsidy that the court of Versailles might attempt to negotiate in any part of the empire for the purpose of securing troops; he was also to make it his duty to understand thoroughly all the grievances under which the protestants in the empire laboured (State Papers, Foreign Office, German States, 1780). Having given satisfaction at Munich, he was appointed minister to the Sardinian court at Turin in succession to Lord Mountstuart (February 1783). At Turin, where he arrived on 15 Oct. 1783 and remained till 1798, Hampden-Trevor spent the rest of his official career. He was here again instructed to give his best assistance to the Vaudois and other protestants within the king's dominions, and deputies from the Vaudois actually waited on him (27 Dec. 1783). He was at first (January 1785) ordered to maintain a strict neutrality in the approaching struggle between France and Austria, and his numerous despatches exhibit the difficulties of the Sardinian kingdom owing to its position between two great powers. In December 1786 he made an ineffectual attempt to secure promotion to Florence. Subsequently, however, he was offered and refused missions to both Russia and Vienna (State Papers, Foreign Office Sardinia 104, 1 May 1789). The title of plenipotentiary, with additional pay, was conferred on him on 16 June 1789; for this he had asked in 1783, urging the ‘very spare diet of his last two stations,’ in which he declared he had spent 4,000l. more than he received from government. From 1793 to 1796 the critical position of affairs kept him constantly at his post. The French occupation of Turin on 3 July 1798 compelled his retirement. He succeeded his elder brother, Thomas, in the peerage as third Viscount Hampden on 20 Aug. 1824, and died without issue on 9 Sept. 1824 in Berkeley Square. He was buried at Glynde in Sussex.
Hampden-Trevor married, 5 Aug. 1773, Harriot (1751–1829), only child of the Rev. Daniel Burton, canon of Christ Church, who survived him. By his death and the failure of issue male of Robert Hampden-Trevor, the Hampden estates passed under the will of John Hampden to the Hobart family.
Hampden-Trevor edited and published at Parma ‘Poemata Hampdeniana,’ a splendid folio edition of some of his father's Latin poems, which was dedicated to George III, under date 1 Jan. 1792.
[Gent. Mag. 1824, ii. 465; Lipscomb's Buckinghamshire; Coxe's Life of Lord Walpole; Collins's Peerage of Great Britain, ed. Brydges, vi. 304; G. E C[okayne]'s Complete Peerage; Hampden-Trevor's Despatches in the Record Office.]