The sitter was the wife of 1st Viscount Melbourne, Gentleman of the Bechamber (1783-1795) and Lord of the Bedchamber (1812-1828) to the Prince of Wales, whose mistress she became. She was the mother of 2nd Viscount Melbourne (1779-1848), the Prime Minister and favourite of Queen Victoria. Lady Melbourne was, according to Byron, not only 'captivating' but 'sagacious'. The date of the portrait, c. 1784, is suggested by the sitter's age and costume. She is shown in a Jacobean fancy dress typical of the Romantic period and of Cosway's art.