John Marshall arrived at the Cape with his family in the Woodbridge on 5 November 1816. That night the ship was driven ashore in Table Bay, but the crew and part of the cargo were saved. During the next month Marshall took up his position as president of the Lombard Bank, established by the Dutch East India Company in 1793 as the first commercial bank at the Cape. He bought a five hectare property, "The Vinyard" in December 1817 and lived there with his wife, two sons and two daughters. In December 1821 he left on a visit to England, and again in February 1825. In 1830 he wrote a letter to the editor of the Cape of Good Hope Literary Gazette, published on 13 October 1830 and also issued as a pamphlet, in which he advocated the establishment of a savings bank. The Cape of Good Hope Savings Bank was subsequently founded in June 1831, with John Marshall as president. However, he also retained his position at the Lombard Bank until that institution closed in 1842.
In 1821 Marshall wrote a Description of a machine denominated the lifting dock, the model of which was exhibited in Table Bay, on Monday, the 3d of December, 1821, a pamphlet of 19 pages published in Cape Town. The author is identified as "President of the Government Bank [Lombard Bank]... formerly a Commander of one of the East India Company's Ships".
Marshall's contribution to meteorology took the form of a letter on the theory of storms which was published in the South African Chronicle in 1825 under the pseudonym "Mercurius". It was reprinted in 1839 as part of a pamphlet, Papers, correspondence, &c, connected with Lieutenant-Colonel Reid's recent publication, entitled The law of storms... (Cape Town, 1839). This pamphlet was issued in response to a request from the British Government to draw public attention to Sir William Reid's book, An attempt to develop the law of storms...(London, 1838). In an introductory letter Thomas Maclear*, astronomer at the Royal Observatory, Cape of Good Hope, gives high praise to Marshall's theory and notes its similarity to that of Reid.
"John Marshall" was a common name at the time and three persons with that name are listed as having lived at the Cape between 1800 and 1819 (Philip, 1981). One of these, described above, was the president of the Lombard Bank. Another was a master mariner who arrived at the Cape with his wife from Madras, India, in January 1809 as master of the Diana while on his fourth tour of duty with the Honorable East India Company Marine Service. However, these two were most likely the same person (Ravestijn, 2016), as has been assumed above. John Marshall the mariner was married to Jane Campbell in Calcutta (now Kolkata) in 1808 (Benthall, 2016), while John Marshall the banker's wife was also named Jane (Philip, 1981).