Thomas Erskine, 9th Earl of Kellie

At a young age, he was sent to Gothenburg to learn a trade. He was employed in 1759 in the office of George Carnegie, a Jacobite exile who had established himself as a merchant there. After a few years, he transferred to the firm of the iron-exporting English brothers John and Benjamin Hall, and became a partner in the firm in 1767. In his 30 years as a partner, he managed to amass a large fortune. In addition to retaining his partnership in the firm of the Hall brothers, Erskine pursued business under his own name, later partnering with David Mitchell from Montrose, who took over Thomas Erskine & Co. as sole owner after Erskine's departure for Scotland.

In 1775 Erskine was appointed British consul for Gothenburg, Marstrand, and the other port cities on the West Coast of Sweden. As such, he wrote regular reports to the British government, including reports on the Swedish contraband trade with France during the revolutionary wars.[3] This position also enhanced his social position in Gothenburg.[4] He was one of the 20 (at the time unmarried and for the largest part British-born) founding members of the Royal Bachelors' Club, an English-type gentlemen's club established in 1769 mainly in order to circumvent a ban on the playing of billiards at public establishments.[5]

Erskine bought back Cambo House in 1790. He spent the winter of 1793–94 in Scotland, but returned to Gothenburg, where he remained as consul and continued his business until 1799. In that year he inherited the Earldom of Kellie from his nephew Charles Erskine.[6] His definite departure for Scotland was troubled by a conflict with the Gothenburg City Council, which demanded that he pay a sixth of his fortune before leaving Sweden.[7]

As Earl of Kellie, Erskine was elected a representative Scottish peer in the British House of Lords in 1804, was re-elected in 1807, and remained such until his death. In 1824, he succeeded the Earl of Morton as Lord Lieutenant of Fife.[8]