Either Sarah Burdon Swinburne Riddell (c. 1731-1817), wife of Sir James Riddell, or Jane Buchanan Riddell (d. 1798), widow of Sir John Riddell.

First letter in correspondence: c. September 1784; G. E. Cokayne, Complete Baronetage (5 vols., London, 1900-06), ii, 352, v, 203.