Before succeeding to his ancestral estate of Blairhall, Campbell served in the East India Company navy, and by 1817, age estimated at 35 (sic), was ‘a ship owner but general agent principally in the East India line’ with offices at Warnford Court, Throgmorton Street, London. His friend Col. John McLeod, at Campbell’s request, recommended him to Lord Melville for ministerial support as candidate for his native district of burghs against Francis Ward Primrose, 9 Aug. 1817. The day before, in making this request to McLeod, Campbell had explained that he was impressed with the success of McLeod’s similar application to Melville on behalf of Thomas Potter Macqueen, son of his ‘best and most intimate friend in this life’ Dr Macqueen, and that he venerated the ‘immortal name’ of the late Lord Melville, ‘the best friend that Scotland and Scotchmen ever knew’. He intended to purchase the Castle Hill estate, which in addition to his virtual command of the burgh of Culross and the employment he gave to colliers would add to his local weight. McLeod assured Melville that although Campbell had spent most of his life in India and London, he had good friends in Scotland and would prefer the notoriously expensive Stirling Burghs to any seat he might buy, ‘although a very prudent, saving wise man’ and likely to prove another (Sir) Robert Wigram I.
On 29 Oct. 1819 his friend McLeod informed Melville that Campbell had been recuperating near Cheltenham from the blow to his health and spirits caused by this disappointment and ‘the cruel manner in which he was betrayed and deceived by whom time will prove’. Despite his disastrous investment, he was likely to preserve his Scottish estate and mercantile house, and his London business at 1 White Lion Court, Cornhill: in fact, he had just been procured by his City friends a contract from the East India Company to build a 1,300 ton ship for the China trade. Nor, claimed McLeod, had Campbell given up his aspirations to the seat for Stirling Burghs.