Imperatrix was a chestnut mare bred by John Pratt and foaled in 1779.
Alfred won several races at Newmarket, including the Clermont Cup and Grosvenor Stakes.
[1] On 24 September 1782 at Doncaster Racecourse, Imperatrix won the two-mile St. Leger Stakes, beating Monk (the evens favourite), Nobleman and two others.
In her only other race she finished second to Miss Kitty in the Port Stakes at Pickering, beating the eight other runners.
[3] Imperatrix then became a broodmare and produced nine foals, including at least three winners.