Stuart-Wortley was commissioned into the 48th Foot in 1790, transferred to the 7th Foot in 1791, and purchased a Captaincy in the 72nd Foot in 1793. He was promoted Lieutenant-Colonel in 1797 and became Colonel of the 12th Foot six months later. In 1797 he transferred to the Grenadier Guards, but resigned his commission in 1801.
Political career
Stuart-Wortley sat as ToryMember of Parliament for the rotten borough of Bossiney in Cornwall between 1797 and 1818, when he was returned for Yorkshire. His attitude on various questions became gradually more liberal, and his support of Catholic Emancipation lost him his seat in 1826. He was then raised to the peerage as Baron Wharncliffe, of Wortley in the County of York, a recognition both of his previous parliamentary activity and of his high position among the country gentlemen. In 1831, as political tempers ran high over the issue of Reform, Wharncliffe succeeded in opening channels of communication between the Government and the Opposition. Greville noted in his diary on 19 November 1831 that:
”Wharncliffe has neither wealth, influence, nor superior abilities, nor even popularity with his own party. He is a spirited, sensible, zealous, honourable, consistent country gentleman; their knowledge of his moderation and integrity induced Ministers to commit themselves to him, and he will thus be in all probability enabled to render an essential service to his country…”
He at first opposed the 1832 Reform Bill but, having come to see the undesirability of a popular conflict, separated himself from the Tories and took an important part in modifying the attitude of the peers and helping to pass the bill, though his attempts at amendment only resulted in his pleasing neither party. He became Lord Privy Seal in Sir Robert Peel's short 1834 to 1835 ministry, and again joined him in 1841 as Lord President of the Council, a post he held until 1845. In 1834 he was sworn of the Privy Council. In 1837 Lord Wharncliffe brought out an edition of the writings of his ancestress, Lady Mary Wortley Montagu.
Family
Lord Wharncliffe married Lady Elizabeth Caroline Mary Crichton, daughter of John Crichton, 1st Earl Erne and his second wife Lady Mary Hervey on 30 March 1799. They had four children:
John Stuart-Wortley-Mackenzie, 2nd Baron Wharncliffe
Hon. Caroline Jane Stuart-Wortley-Mackenzie, married on 30 August 1830 Hon. John Chetwynd-Talbot
Lord Wharncliffe died in December 1845, aged 69, and was succeeded in the barony by his eldest son, John, whose son Edward, 3rd Baron was created Earl of Wharncliffe in 1876. Lady Wharncliffe died in April 1856.