West India merchant (Colonial - Caribbean)
https://eap.bl.uk/sites/default/files/legacy-eap/downloads/eap345_survey.pdf p. 13
Partnership of Thomas Plummer and Thomas Foster Barham as Plummer & Barham of London expired 30/4/1802; business to be carried on by Thomas Plummer, John Foster Barham and John Plummer as Plummer, Barham and Plummer. Firm was West India merchant with interests in shipping and insurance. Firm usually called Plummer, Barham and Plummer; based, successively, at 2 Fen Court, Fenchurch Street, 2 Philpot Lane, Thames Street, and, by 1816, 32 Fenchurch Street.
According to the History of Parliament, Joseph Foster Barham was a partner until 1815; followed by his brother John Foster Barham. Joseph Foster Barham II's partnership has yet to be confirmed by LBS. It appears more likely that Joseph succeeded John rather than vice versa.
London Gazette 15477 4/5/1802 p. 458
Fisher (ed.), House of Commons 1820-1832, vol. 6 (entry for John Plummer).