Henry Douglas: the winning jockey in 1829 and 1831 in the Magyar Kancadíj (Hungarian Oaks)

[William Douglas]

The records of the Magyar Kancadíj (Hungarian Oaks) show that the winning jockey in 1829 and 1831 was Henry Douglas, riding the fillies Manfred (1829) and Fortuna (1831). In the early winner lists, the format is horse name followed by the jockey's surname, appearing as"Manfred–Douglas" and"Fortuna–Douglas." 

From Hungarian racing histories, Henry Douglas is remembered as one of the pioneering British horsemen who helped establish organized horse racing in Hungary during the reform era inspired by Count István Széchenyi. Contemporary and later accounts identify him as an English jockey and horse trainer who settled in Hungary in the 1820s and became involved with some of the earliest Hungarian flat races. The Hungarian Oaks itself was founded in 1829, making Douglas one of the first winning riders in the history of Hungarian classic racing. 

Regarding his background, I found references connecting a Henry Douglas with England and with horse training in Hungary, but the sources I located do not provide a definitive birth date, parentage, or a full biographical sketch. What can be verified from the racing records is that he was active in Hungary at the very start of organized thoroughbred racing and won the first and third runnings of the Hungarian Oaks.

Can anyone throw light on this individual?