The sitter, traditionally identified as Lady Diana Howard, is believed to be the daughter of Henry Howard, 5th Earl of Suffolk (1627-1709) and his wife Mary Stuart daughter and heiress of Andrew, 3rd Lord Castle Stuart (d. 1650). Lady Diana's three brothers were all successive Earls of Suffolk; Henry 6th Earl (1670-1718); Edward, 8th Earl (1672-1731), following the death of his nephew; and Charles 9th Earl (1675-1733). The date of her birth is not recorded but it must be assumed that she was born during the 1670s, making her age in the present picture, dated 1685, between five and ten years. She is recorded as having married a Colonel John Pitt who, at the time of publication, is untraceable in the Pitt pedigrees. John Le Neve records her being the daughter of Henry, Earl of Suffolk and Bindon [sic], and wife of Colonel Pitt, dying in London in June 1710 and being buried at Saffron Walden in Essex [J. Le Neve, Monumenta Anglicana, London, 1700-1715, p. 204].

J. Douglas Stewart (Sir Godfrey Kneller and the English Baroque Portrait, Oxford, 1983, no. 272, fig. 55a) records a Portrait of a Lady Diana Fielding, signed and dated 1697, and inscribed 'Lady Diana Howard'. The sitter of this portrait married Thomas Howard of Ashtead (d. 1701) in the 1680s and had a son by him, Thomas, who died in 1703 aged fifteen - thus ruling her out as the sitter in the present picture.