Partner from 1793 until his death.
Bryan Edwards, John Simpson, Samuel Harrison and Martin Maddison formed a new partnership in 1793 after Christopher Shaw had left an earlier partnership trading as Southampton Bank with John Simpson and Martin Maddison.
The co-partnership between Bryan Edwards, Samuel Harrison, John Simpson and Martin Maddison was dissolved 31st December last [i.e. 1798]. The business was carried on by Samuel Harrison, John Simpson and Martin Maddison [the elder].
Martin Maddison [the younger] and Robert Pearce were trading as the Southampton Town and Country Bank in 1844.
Sotonopedia says that Maddison, Pearce and Hankinson in 1869 merged with the Southampton and Hampshire Bank to form the 'Union Banking Company', a predecessor of Lloyds. The Lloyds Banking Group Archives online index shows Grant & Maddison Union Banking Company taken over by Lloyd's in 1903, and says Grant & Maddison Union Banking Company was established in 1869.
London Gazette 13582 15 October 1793 p. 918.
London Gazette 15116 16 March 1799 p. 255.
London Gazette 20374 16/08/1844 p. 2857.