Moved to London (c. 1759), where he was socially and financially successful. A supporter of the American colonies in their dispute with the British, Sayre was arrested and imprisoned in the Tower of London (1775).
Went to Paris. Arthur Lee engaged him as his secretary for the mission to Berlin (1777).
Born in Southampton, Long Island. Married in 1775 to Elizabeth Noel; in 1790 to Elizabeth Dorone.