Slieve Gallion's colour was controversial: he was officially described as a black horse,[2] although his portrait suggests that he was a dark-coated bay,[1] and some argued that he was an unusually dark chestnut.

A much anticipated meeting between Slieve Gallion and the year's other leading colt, Traquair, in the July Stakes at Newmarket did not come to pass when Greer's horse was withdrawn.

He was made favourite at odds of 1/4 in a field of five runners[8] but was beaten after a "long and desperate struggle"[9] by Eustace Loder's colt Galvani, with Traquair third.

[10] Although he had been beaten in his most important test, Slieve Gallion was widely regarded as the fastest two-year-old of the season, despite his "tearaway"[11] racing style and tendency to carry his head at a high, awkward angle.

Ridden by Billy Higgs, he took an early lead and after being briefly challenged by Bezonian drew clear "in splendid style" to win easily by three lengths.

[17] Shortly after the Derby, Orby's owner "Boss" Croker challenged Greer to a match race between the colts for "a substantial sum" over any distance.

[18] Two weeks after his defeat at Epsom, Slieve Gallion returned to the one mile distance for the St James's Palace Stakes at Royal Ascot which he won from two opponents at odds of 1/20.