Arnull hailed from a family of jockeys that dominated British horse racing in the latter part of the 18th century and early 19th.
For example, in spite of the fact he found that "wasting was a sore burden ... [he] performed the unrivalled feat of knocking off 7 lbs in a single day" to meet the weight for a horse he wanted to ride.
At the time it merited but a small notice in the London Evening Post of 6 May 1780[7] but in retrospect was said to have "fairly caught hold on the public imagination".
[8] Arnull is said to have been seen going to post wearing: a black velvet 'cap with a long French peak, and a bow of black satin riband behind long hair falling to the shoulders, a white cambric handkerchief, in ample folds, tied at the back; a long body coat with flaps, wide skirts opening at the sides as well as before and behind knee-breeches strapped just below the knee white cotton stockings, Oxford shoes and silver buckles[7]His main rival in the race was Colonel O'Kelly's Boudrow,[7] also recorded as Budroo,[8] who came in second.
[9] At Nottingham the following year, suspicion turned on Arnull when Diomed lost to what was considered "a very far inferior horse",[7] losing Bunbury a large sum of money.