The sitter was the daughter and heiress of General Thomas Warburton of Winnington, Cheshire, and his wife, Anne, grand-daughter of Sir Robert Williams, 2nd Bt., of Penrhyn, and eventual co-heiress to the estates of Penrhyn, Carnarvonshire. In 1765 she married Richard Pennant (d.1808), second son of the Liverpool merchant John Pennant. By this marriage the estates of Penrhyn were re-united since his father had purchased from the family of Sir Walter Yonge, the part of the estates that Lady Yonge had inherited. Richard Pennant became M.P. for Petersfield (1761-67) and later Liverpool (1767-80 and 1784-90). He was also responsible for developing the Penrhyn slate quarry which gave an important impetus to the Welsh slate trade. He was created Baron Penrhyn in 1783, but the title became extinct on his death in 1808. Anne died childless at Penrhyn Castle in 1816, and the estates of Penrhyn passed to her husband's cousin, George Henry Dawkins.