Jaffray, a native of Stirling, was possibly a relative of Henry Jaffray, provost of Stirling like other Jaffrays before and after him, who died in 1799. Early in life he went to America and was a loyalist in the war of independence. He entered government service and in 1780 and 1784 was at Montreal sending instructions to commissaries general. He informed Pitt in 1797 that he had been 22 years in the public service ‘and acquired by practice and observation more knowledge of the business of an army’ than most men.
In 1802 Jaffray surfaced as a would-be purchaser of a seat in Parliament. His income tax assessment had been £200. (Sir) William Pierce Ashe A’Court, to whom he had applied for a seat, passed on his credentials to Lord Radnor, adding, ‘I have not seen him, but believe he is inclined to bid high’. At the last minute he found an opening at Retford after a contest, on the Newcastle interest. He was an inconspicuous Member. No speech or minority vote is known. He was listed ‘doubtful Addington’ in September 1804 and, despite a vote against the censure of Melville, 8 Apr. 1805, ‘doubtful Sidmouth’ in July. He disappeared from view thereafter. According to Oldfield he went bankrupt, perhaps as a partner of George Baillie of Finsbury Place, Middlesex.