In 1847, John Barham Day moved away from Danebury, leaving the stable to his son John. Shortly afterwards, William, having been reinstated by the Jockey Club, set up as a trainer near the village of Woodyates, on the border of
Dorset and
Wiltshire. In 1852, he trained his first major winner when he sent out Joe Miller to defeat forty-two rivals the
Chester Cup, at that time one of the year's most important and valuable races. A month later the same horse won the
Gold Cup at
Royal Ascot. In 1855, the Day family appeared to have three of the best three-year-old colts in England: William trained Lord of the Isles for
James Merry, his father trained
Henry Padwick's St Hubert, while John, Jr.'s classic candidate was a colt named Kingstown. According to one version of events, A third Cambridgeshire win with Catch 'em Alive followed in 1863 and in 1869, Day won
The Oaks and
Ascot Gold Cup with the
filly Brigantine. For a time, Day was employed as a private trainer by Brigantine's owners
Frederick Johnstone and
Henry Sturt. Other important wins in major handicaps included two
Stewards' Cups, three
Royal Hunt Cups and a
Lincolnshire Handicap. After a relatively quiet period in the 1870s, Day had his last big success with the Kentucky-bred Foxhall who was sent to England in 1880 by his owner
James R. Keene. Foxhall was not entered in the classics but established himself as one of the best horses in Europe by beating
Tristan in the
Grand Prix de Paris in June 1881. Later in the year he won both legs of the Autumn Double. Day was unable to travel to Newmarket to witness the Cambridgeshire, being confined to bed with a broken
collarbone, but nevertheless took more than £10,000 in winning bets. The following year, Foxhall won the Ascot Gold Cup but was beaten when odds-on favourite for the
Alexandra Plate. The relationship between Day and Keene appears to have broken down at this point, with critical articles appearing in both the British and American press. Keene's horses were removed from Day's stable and sent to Richard Marsh at
Newmarket, Suffolk. ==Retirement==