Christie's lot notes follow, "The sitter, the daughter of Thomas Pitt, 1st Baron Camelford (1737-1793) and sister and sole heiress of her brother Thomas Pitt, 2nd Lord Camelford, married her cousin, the Whig politician and later Prime Minister William Wyndham Grenville, 1st Baron Grenville (1759-1834), in 1792, uniting the Pitt and Grenville political dynasties. This picture is first recorded at Dropmore, Buckinghamshire, which Grenville bought in the year of his marriage. In 1804 the sitter inherited Camelford house in Oxford Street and Boconnoc in Cornwall, with estates in excess of 20,000 acres. Their marriage was childless and on Lady Grenville's death her estates devolved by her will on her husband's nephew the Hon. George Fortescue (1791-1877). Her husband also sat to Hoppner." Her article in thepeerage is here.