Foaled in 1819 by Woful out of Rosalind (Blacklock's dam) by Coriander, Theodore won the St. Leger in 1822 for his owner the Hon. Edward Petre. Theodore was badly lame before the race and started at 200-1, indeed his jockey John Jackson is said to have burst into tears when told that he had to ride a horse with such bad odds. He went on to win the Manchester Gold Cup in 1824, and was sold to Mr. Carleton, for whom he won the Gold Cup and Members Plate at Edinburgh in 1825.
The Hon. Edward Petre was a great patron of the turf. Theodore was his first classic winner. He bred and owned the famous filly Matilda who won the 1827 St. Leger, the first of his three consecutive victories, followed by The Colonel in 1828 and Rowton in 1829.
John Jackson, was one of the best Jockeys of his time, riding only in the north, he enjoyed a long and successful career. His St. Leger win on Theodore was his eighth win in the great race.