A landowner and former merchant, Leslie was a Conservative who was not afraid to give credit to his political opponents when it was due. He was one of a number of MPs representing constituencies in north-eastern Scotland in the 1860s who had East India and Chinese connections, others including the Liberals William Henry Sykes, MP for Aberdeen, 1857-72, and James Dyce Nicol, MP for Kincardineshire, 1865-72.
Leslie was descended from the Leslies of Garioch, who traced their lineage back to the eleventh century. His father and namesake had succeeded his uncle as the 10th laird of Warthill in 1799.
Leslie was returned for Aberdeenshire at the 1861 by-election, after declaring his support for reciprocal free trade and a non-interventionist foreign policy.
Leslie voted with the Conservative leadership in the key party votes of the early 1860s, opposing Gladstone’s repeal of paper duty, 30 May 1861, and backing Disraeli’s censure motion on the government’s Danish policy, 8 July 1864. On religious issues, he opposed the abolition of church rates and religious tests for English universities and supported the anti-Maynooth motions of George Hampden Whalley. He favoured legislation to ensure a strict observance of the Sabbath.
In his maiden speech, he lobbied for the government to grant public money for new buildings at King’s College, University of Aberdeen, 12 Apr. 1861. An occasional speaker, most of Leslie’s other speeches were brief, technical points on proposed legislation, particularly regarding Scottish matters. For example, in the 1862 debates on salmon fisheries, an important sector in the Scottish economy, Leslie successfully proposed a sixty rather than a thirty-six hour break from fishing over weekends.
Leslie was returned unopposed at the 1865 general election after modifying his stance on key issues to placate local farmers. He now favoured exempting hares and rabbits from the game laws and altering, if not abolishing, the law of hypothec.
Leslie displayed a similarly unpartisan streak by defending the Liberal government from blame for the spread of the cattle plague, during the debate on the Queen’s speech, 6 Feb. 1866. The government had taken the only course ‘befitting the free institutions of their country’ and empowered local quarter sessions to act.
That vote proved to be Leslie’s last act of significance in Parliament as he resigned unexpectedly in early May due to his own ill-health and that of other members of his family. In later life he was affected by paralysis and he died in 1880. A local obituary noted that his political career ‘increased his reputation as a man of solid judgment and splendid business capacity’. As he had been predeceased by his two sons, the entailed Warthill estate passed to his eldest daughter Mary Rose, who was married to George Arbuthnott, of Elderslie, Surrey, an officer in the Scots Greys.
