The Duke of Newcastle Stud papers show that the 2 daughters of Blacklegs Royal Mare in the GSB, including this Oxford Dun Arabian mare, were probably actually out of her daughter, Darcy's Sorrill Royal Mare

Dam of of the great broodmare Miss Slamerkin, through which the maternal line of the family continues and dam of top class racehorses Bustard (1747 King's Plate Newmarket), [Portmore's] Othello (1749 King's Plates Salisbury, Canterbury, Lewes, Newmarket, 1752 King's Plate The Curragh) and the great Duchess (1753 King's Plates [mares] Hambleton and Newmarket, 1754 King's Plates Nottingham, York,

Lincoln, Newmarket, 1755 King's Plate Newmarket), and ancestress of many top class racehorses including Saltram (1783 Derby), Annette (1787 Oaks), Beningborough (1794 St Leger), [Williamson's] Ditto (1803 Derby), Pan (1808 Derby), Gustavus (1821 Derby), Mundig (1835 Derby), Cotherstone (1843 2000 Guineas, Derby), West Australian (1853 2000 Guineas, Derby, St Leger) and Wild Darrell (1855 Derby)