By 1754 Bristow was perhaps the foremost British merchant in the Portugal trade which through Lisbon extended to Spain, South America, and the West Indies, and was one of the leading figures in the South Sea Company. In partnership with Peter Burrell I he held important Government contracts: 1740-56, for remitting money for the forces at Gibraltar and in Minorca (generally about £200,000 p.a.); and 1741-56, for provisioning the troops in Minorca. He was also a considerable underwriter of Government loans.
In Parliament Bristow sat as a regular Government supporter, from 1734 till 1761 on the interest of his brother-in-law, John, 1st Earl of Buckinghamshire (who died in 1756). Bristow’s position was much impaired by the very severe losses which he suffered in the Lisbon earthquake of 1 Nov. 1755, and from which his firm never altogether recovered.
In 1761 he was returned for Arundel with Government support,
Received a letter from Mr. Bristow to the Duke of Newcastle acknowledging his inability to supply the garrison [at Gibraltar] with the sums due from the money advanced to him for that service ... The money advanced to him and not remitted by him was reduced to about £18,000 but as probably the paymaster would draw more bills and he was not able to discharge the same he found himself obliged to apply ... for an indulgence of time.
A memorial from Bristow of 31 Aug.
