Petty, John Henry (1765–1809), Earl Wycombe , 2nd marquess of Lansdowne , politician, was born 6 December 1765, eldest son of William Petty (qv), politician, 2nd earl of Shelburne and later 1st marquess of Lansdowne, and his first wife, Lady Sophia Petty (née Cateret). Educated privately, he entered Christ Church, Oxford, in 1783 but left after a year to embark on the grand tour (1784–90). Styled Viscount Fitzmaurice until 1784, he received the courtesy title Earl Wycombe (1784–1805) when his father was raised in the peerage. Shelburne had great plans for him and attempted, in Lady Holland's words, to make him ‘a tool for his ambition, and to live over again in his political career’ (Hist. parl.: commons, 1790–1820, v, 789). Wycombe soon grew to resent this influence, and never really established himself in parliament; his father had returned him for his old seat at Chipping Wycombe in May 1786 and he represented the constituency half-heartedly until 1802.
Becoming more active in politics in the 1790s, he impressed the whig opposition with his liberal sentiments, but never threw off the suspicion that he was his father's mouthpiece. He became the friend and supporter of Charles James Fox and a sharp critic of his father's former protégé, William Pitt. Tiring of politics, he decided to live abroad and spent three years in Italy and Switzerland (1794–7). He returned in 1797 for a confrontation with his father, who had heard numerous reports of his misdeeds on the Continent. Becoming increasingly eccentric and embittered, Wycombe was, it seems, determined to sabotage his own career to hurt Shelburne. He remarked in 1798 that there was ‘scarcely an error or misfortune in my life which I cannot trace directly or indirectly to my father’ (Hist. parl.: commons, 1790–1820, v, 789). He spent most of the period 1798 to 1803 in Ireland, resigning his commons seat in 1802. Purchasing a villa at Sandymount, he kept Fox and the British whigs informed about Irish affairs, and lived with what he described as his ‘sporting heifer’ of a mistress called Rosy (Pakenham, 102).
Associating with members of the United Irishmen, according to one account he ‘conducted himself in such a manner . . . that the government thought it necessary to inform his lordship that if he did not quit Ireland he would be taken up’ (G.E.C., Peerage, 439). He remained in Ireland despite this threat, and in 1803 became involved in Robert Emmet's (qv) plans for an insurrection, apparently even visiting the rebels' depot at Thomas St. When the rebellion failed he offered to assist James Hope's (qv) flight from Ireland and once again fell under the suspicious gaze of Dublin Castle. Francis Higgins (qv) apparently wanted to unmask him as a ‘covert traitor’ (Madden, iii, 359), and Wycombe became terrified that he would be arrested. On 10 December 1803 he wrote to the chief secretary, William Wickham (qv), asking if a warrant of arrest had been issued in his name and was relieved to discover that this was ‘utterly unfounded’ (BL, Add. MS 35704, f. 243). It seems the government had decided against prosecuting the son and heir of a former British prime minister on limited evidence.
Returning to Britain he succeeded his father as 2nd marquess of Lansdowne on 7 May 1805. Immediately he married his latest mistress, Maria Arabella Gifford (née Maddock), widow of Duke Gifford of Castle Jordan, Co. Meath; they had no children. He spent his final years at Southampton, where he abandoned his radical principles and offered his support to the government. At a royal reception the king described him as one of the best-bred men he had ever met. He died at Berkeley Square on 15 November 1809. Writing about him some years later, Lord Holland remembered him as ‘a very accomplished man, with much general knowledge’, but acknowledged that his fatal flaw was his closed and suspicious nature: ‘he had perversely persuaded himself, and some errors of his education had taught him, to guard against every kind of affection of the heart’, even though this was ‘a quarter in which he was not by nature very vulnerable’ (Hist. parl.: commons, 1790–1820, v, 789).