Son of George Fordyce and Elizabeth Brown. Married (1770) to Margaret Lindsay (1753?-1814), daughter of James Lindsay, the Earl of Balcarras.
In the mid-1760's, Fordyce became a partner in a London bank, henceforth known as Neale, James, Fordyce, and Downe. Fordyce quickly gained a reputation as a highly successful banker and investor. However, some of his dealings went wrong, and, unbeknownst to his partners, he used the profits from other investments to cover the losses. The bubble burst in 1772, when the bank went bust, "starting a chain of bank failures that looked, for a while, like the beginning of an international collapse". On June 9, 1772, Fordyce fled to France. Later that year, he returned to England, declared personal bankruptcy, and in December had agreed a repay scheme with his creditors. In 1780 he ran, unsuccessfully for parliament.1
According to Henry Hamilton in The Economic History Review2
"The leading partner [in Neale, James, Fordyce, and Downe] Alexander Fordyce, had made a large fortune on Change Alley, and when he became deeply involved in speculation in East India stock he used his bank deposits to pay his losses. The Bank of England, alarmed at the growth of speculation, adopted a policy of selective limitation of its discounts. This applied particularly to Jews with Amsterdam connexions and later to Scots paper. The immediate cause of Fordyce's ruin was the refusal of the Bank of England to discount his bill on an Amsterdam jew.
The plays The Bankrupt by Foote, and The Man of Business by Colman were both directly inspired by Fordyce's dealing in connection with the bank failures.
Boswell had tea with Fordyce in Edinburgh on November 6, 1762. He described Fordyce as "a man of estate, of good business as a banker and good parts and a good heart". They also met a few times in London in the following year.