Stuart, by the will of his grandfather (who died in 1761), was designated next heir after his mother to the vast Wortley fortune, failing legitimate issue of his disinherited uncle, Edward Wortley Montagu. An idle undisciplined youth, he was sent to Edinburgh to board with Principal Robertson.
It was disagreeable to Lady Bute to have him named for that he had behaved very ill since he went to France ... and had spent a prodigious deal of money ... but there was one thing worse than all, for that, after having assured his father that there was no truth in the report of his marriage, it now came out he was married and had taken such an aversion to the lady, that he wrote to his father to entreat him ... to extricate him out of the dreadful difficulty ... thinking it might be in his friends’ power to break the marriage, which as it was in Scotland, is impossible. The reason he gives for having taken such a dislike to his wife is that he was drawn in ... and ... now declares he will never live with her.
At the general election of 1768 Stuart was returned in absentia for Ayr Burghs. In July, after his return from France, Lady Mary Coke recorded that Bute ‘would not see him till he promised to be reconciled with his wife ... and they are to make him a settlement’.
Having supported in 1775-6 Mountstuart’s abortive bill for a Scottish militia, Stuart in 1778-9 served as a lieutenant-colonel in the Bedfordshire militia.
Stuart voted against Shelburne’s peace preliminaries, 18 Feb. 1783; supported the Coalition; and opposed Pitt’s Administration. Thomas Coutts wrote to Charles Stuart, 23 Jan. 1784: ‘Lord Mountstuart and his brother adhere to Mr. Fox which I believe Lord Bute by no means approves of ... he loves the King so much he cannot bear to see any of his family go counter to him.’
He died 1 Mar. 1818.
