George Thompson, merchant and traveller, was a son of Thomas Thompson, a prosperous farmer, and his wife Isabel Hetherington. He made a voyage to Rio de Janeiro as a sailor, and afterwards worked for some time as a draper and then a solicitor's clerk. In September 1818 he arrived in CapeTown, probably to open a branch of the London merchant firm Borradaile Sons, and two months later received official permission to settle in the colony as a trader.
In January 1821 Thompson set out on a six week journey to the eastern Cape to investigate the possibilities of expanding trade with the British settlers of 1820. He travelled by sea to Port Elizabeth, visited Uitenhage, Grahamstown, Bathurst, and other settlements and returned to Cape Town overland. From April 1821 to March 1822 he visited England and on the way there attended Napoleon's funeral on St. Helena on 9 May 1821. A few months after his return he visited the wreck of the Grace, which had stranded near Cape Agulhas in June 1822. In August that year he left Cape Town on a journey to Swellendam and George to investigate the commercial resources of the region and particularly the growing exportation of aloes. He also visited the Cango Cave. From April to July 1823 he undertook a journey to the eastern frontier of the colony. From there he proceeded up the Fish River, via Cradock and Graaff-Reinet, across the Sneeuberge to the Orange River and on to Griqua Town. Proceeding to Kuruman he visited the recently abandoned site of Lattakoo. On the return journey he visited the Cango Cave for the second time on 4 July. He was only the third person to provide a description of the cave (George Thom* had described it in 1816). His account was published as "Description of a grotto in the interior of the Colony of the Cape of Good Hope" in the Quarterly Journal of Science, Literature and the Arts, 1823, Vol. 16, pp. 272-274).
In July 1824 Thompson set out again to investigate the Orange River as a possible trade route into the interior. He reached the river via the Roggeveld and the Hantam and travelled downstream to Augrabies Falls, of which he provided the first published description. After travelling further downstream to Pella he returned to the Cape after five weeks, having made detours to St Helena Bay and Saldanha Bay. His travels served both his business interests and to satisfy his curiosity. The notes and journals he kept during his travels were written up in the form of a book, Travels and adventures in southern Africa (London, 1827, 2 vols) which includes descriptions of all the different tribes he met with. The writing was done by Thomas Pringle, a local poet, journalist and philantropist whom Thompson had supported in his struggle with Governor Charles Somerset. Pringle included some of his own poems in the text, as well as information relating to the British settlers. An annotated edition of the work was published by the Van Riebeeck Society in 1967-8. Thompson's description of the lower Orange River region has been recognised as the best to be published during the early nineteenth century (Mendelssohn, 1910). His book is furthermore valuable for its excellent engravings (some by the naturalist Clemenz H. Wehdemann*), plans of Cape Town and Graaff Reinet, and an adequate though unremarkable map of South Africa which depicts the rivers in the western half of the country, but only the mouths and lower regions of rivers along the east coast. The last part of the book deals with the state of the colony, its agriculture, and prospects for immigration. In later years a letter by him, "Fall of meteorolites at the Cape", was published in the Philosophical Magazine (1839) and in several other European journals.
Thompson visited England and continental Europe from February 1826 to June 1827. In February 1830 he accompanied Charles C. Michell*, surveyor-general and civil engineer at the Cape, on a trip to the Tulbagh district in connection with road building. Another member of the party was the soldier T.H. Duthie, who described the journey in his journal. On 26 June that year Thompson married Johanna M.D. Deneys, with whom he had one surviving son (also named George) and five daughters.
Thompson's role in the cultural life of Cape Town is indicated by his membership of various voluntary organisations. When the South African Literary Society was first formed in August 1824 (with Thomas Pringle as one of its initiators), Thompson was one of the foundation members. However, Governor Somerset refused permission for the society to function. It was eventually established only in 1829, with Thompson again a foundation member. He belonged also to the South African Institution (also established in 1829), the first purely scientific society in southern Africa, and served on its council. After these two societies amalgamated in 1832 to form the South African Literary and Scientific Institution he served on its council from about 1835 to 1841, and as a member of its Statistical Committee from about 1835 to 1838. He was a shareholder of the Cape of Good Hope Association for Exploring Central Africa (which financed the expedition into the interior of Dr Andrew Smith*) and a member of its original management committee. From about 1837 to 1840 he was a member of the committee of the Cape of Good Hope Agricultural Society. He supported the establishment of a botanic garden for Cape Town in 1845 and four years later subscribed £1 per annum to the venture. In 1851 he was one of the exhibiters from the Cape Colony at the London Exhibition. He was also a director of the South African Public Library.
During the 40 years he spent at the Cape Thompson remained associated with the London merchant Borradaile. From about 1824 their partnership was named Borradaile, Thompson & Pillans (who were the treasurers of the Cape of Good Hope Association for Exploring Central Africa), and from about 1851 Borradaile, Thompson and Hall. Thompson was a foundation member of the Commercial Exchange, established in Cape Town in March 1822. In 1854 he became a director of the Cape of Good Hope Mining Company which held leases in the copper fields of Namaqualand. The next year, on behalf of the company, he applied for mining rights in Great Namaqualand (now part of Namibia). At that time he was a director also of the Cape of Good Hope Bank. In August 1859 he published an article on "The survivors of the Grosvenor" in the Cape Monthly Magazine.
He returned to England with his family in November 1859 and settled in London. From there he continued his business activities in the Cape Colony and showed much interest in its political affairs. He advocated the re-annexation of the Free State by Britain and the formation of a confederation in southern Africa, writing many letters to the Colonial Office in this regard between 1866 and 1876. He was a kind and friendly man, and a keen observer.