 He rode many horses for his father whose training facility at Danebury, near Stockbridge in Hampshire was one of the largest and most successful in England.In 1844 he rode The Ugly Buck, owned and trained by his father to win the 2000 Guineas at Newmarket.In 1846, John Barham Day moved away from Danebury to take up a post as private trainer to Henry Padwick, leaving John Jr. to take over the Danebury stable.