He was the youngest son of Provost George Fordyce (1663–1733) of Aberdeen, and brother to David Fordyce, James Fordyce, and William Fordyce. He was educated under his uncle, Thomas Blackwell the younger, and was then for some time in the hosiery trade at Aberdeen. He went to London, and found a situation as outdoor clerk to a banker named Boldero. Eventually he became the most active partner in the firm of Neale, James, Fordyce, & Down.
Banker and speculator
Under his guidance the firm speculated freely, and gained by obtaining early intelligence of the signature of the preliminaries of the Peace of Paris in 1763, and when East India Company stock rose greatly in 1764–5. With the proceeds of these and other speculations Fordyce purchased an estate and built a fine house at Roehampton, where he lived magnificently.
He stood as a candidate for the borough of Colchester at the general election of 1768, and spent nearly £14,000; but was defeated by twenty-four votes. After this he spent money to build a hospital and otherwise cultivate the borough. In 1770 he married Lady Margaret Lindsay, second daughter of James Lindsay, 5th Earl of Balcarres.
The tide of fortune then turned; Fordyce lost heavily at the beginning of 1771 in the fluctuations of the market caused by the dispute with Spain about the Falkland Islands. His partners became alarmed, but it is said he succeeded in quieting their fears by showing them a pile of bank notes which he had borrowed for the purpose for a few hours. His losses continuing, he absconded, and the bank stopped payment on 10 June 1772.
Financial crash and aftermath
The stoppage precipitated a crisis, after a few days, when a major panic arose in the City of London. Sir Richard Glyn and Sir Thomas Hallifax stopped payment temporarily, and a stoppage by Sir George Colebrooke came close.
Fordyce, supposedly in danger from the mob, returned and went through an examination at the Guildhall. His debt was about £100,000.
Fordyce was again the defeated candidate at Colchester in 1780. He died 8 September 1789, at Mr. Mead's in George Street, Portman Square. A sermon by Thomas Toller, minister sharing a church with James Fordyce, published in London in 1775, describes Fordyce's fall. His widow married in 1812 Sir James Bland Burges.