Le Chevalier D'Éon, a man who passed as a woman. Stipple engraving by T. Chambers after R. Cosway, 1787.

The sitter was born of a noble family on 5 October 1728 at Tonnerre. He received an excellent education, and by 1758 was a well-known man of letters in Paris. Physically he was so fine-featured as to be able to pass easily as a woman, which enabled him to create 'Mademoiselle Lia de Beaumont' - his cover as spy for the 'Secret du Roi'. It was in this guise that he carried out several important and successful missions into Russia. However, so convincing was his adoption of the female persona that by 1769 serious speculation as to his true sex resounded throughout France and England, overshadowing his many involvements and accomplishments. The sitter died in England on 21 May 1810, and autopsy revealed finally that he was a man. Ultimately it was not the courageous officer, nor the fine diplomat, nor the man of learning that formed his reputation, but the long standing mystery over his sex