Devaynes was of Huguenot extraction and had spent some of his earlier years in Africa: supporting the Sierra Leone bill, 30 May 1791, he boasted that ‘few men’ had had ‘an opportunity of knowing so much of the country as he did’. By 1790, when his wealth enabled him to retain his seat for Barnstaple at the contested general election, he was firmly established as a leading figure in the City and at East India House, where he supported Dundas and acquired a reputation as a placemonger.
He was defeated at Barnstaple at the general election of 1796, but obtained a seat for Winchelsea on the Barwell interest soon afterwards. He voted for the assessed taxes augmentation bill, 4 Jan. 1798, and was teller for the minority who divided against the compulsory clause of the London dock bill, 28 June 1799. As a subscriber to the proposed London bread and flour company, he was compelled on a point of order raised by Sheridan in the debate on the incorporating bill, 5 July 1800, to declare his interest, and his vote in the earlier division was accordingly nullified. An active philanthropist, he welcomed the bill raising an additional rate in Marylebone and St. Pancras, 1 July 1800, as a necessary contribution towards the relief of the poor.
Devaynes, who in 1801 inherited £50,000 from his elder brother the King’s apothecary,
In 1806 he married a woman said to be ‘60 years younger than himself’ and Farington later heard that ‘he made a settlement upon her which was every year that he lived to have some increase, thereby making it her interest to keep him alive as long as she could’. She succeeded for almost four years and he died 29 Nov. 1809, ‘aged 79’. The terms of the will, in which he made provision for a mulatto daughter and the son of his own illegitimate son, one Benjamin Devaynes of Liverpool, suggested that his personal wealth was considerable, but the bank had been courting disaster for some time and it failed within a year of his death.
