What is "special duty"

Special Duty (foaled 12 February 2007) is a British-bred, French-trained champion Thoroughbred racehorse and broodmare. She won two of her four starts as a two-year-old including the Group One Cheveley Park Stakes and the Group Two Prix Robert Papin and was named European Champion Two-year old Filly at the Cartier Racing Awards. As a three-year-old she recorded a rare double when taking the British Classic 1000 Guineas at Newmarket and its French equivalent, the Poule d'Essai des Pouliches at Longchamp. What made the achievement more unusual was that in both classics she crossed the line in second place and was awarded the victory following a disqualification.