Grant came to England when his father left India in 1790 and entered Cambridge at the same time as his elder brother Charles. Their distinguished university careers ran remarkably parallel and both made their first essays in oratory in the Edinburgh Speculative Society, although Henry Cockburn recalled that neither particularly shone. Grant practised on the western circuit before becoming a commissioner of bankrupts. In 1804 his father’s close friend William Wilberforce utilized his ‘familiar acquaintance both with the languages and the writers of antiquity’ in the preparation of anti-slave trade propaganda.
His brother had been a Member of Parliament for almost seven years and a junior minister for over four when Grant was returned for Elgin Burghs in 1818 by Francis Grant, acting chief of the clan, who operated a system of alternating nomination with Lord Kintore. He supported government, voting against Phillimore’s Marriage Act amendment bill, 26 Apr., and for the foreign enlistment bill, 10 June 1819. In both The Times and the Morning Chronicle he was listed among the ministerial majority against Tierney’s censure motion, 18 May, but his name does not appear in the list subsequently published in Parliamentary Debates. He spoke in defence of the foreign enlistment bill, 21 June, and was a government teller in the division. He was a member of the committee of inquiry into Scottish burgh reform, 7 May. On 24 Dec. his father informed James Grant of Bught that in the recent debates on the government’s repressive legislation both his sons had been ‘repeatedly shut out though presenting themselves for speaking—Robert three times in the course of last night’, when he gave a silent vote for the banishment clause of the blasphemous and seditious libels bill.
Lord Teignmouth, a close friend of the family, wrote that Grant, like his brother, was prone to bouts of ‘languour and lassitude’, but that ‘of the two Robert was unquestionably the more energetic and vivacious’.