[1] Lord Portal, who owned Sun Castle throughout his racing career sent the colt to be trained at the Freemason Lodge stable in Newmarket, Suffolk by Cecil Boyd-Rochfort.
[7] Sun Castle failed to win in two races as a two-year-old but showed promising form in defeat and was rated the fourth-best juvenile of the year in the Free Handicap.
[9] At the end of August, Sun Castle won the St Simon Stakes (not the current race of the same name) at Newbury Racecourse, beating Devonian and Masarin.
Ridden by Georges Bridgland, Sun Castle started at odds of 10/1 in a field of sixteen runners which also included Owen Tudor, Lambert Simnel and the 1000 Guineas winner Dancing Time.
[13] In their book A Century of Champions, based on a modified version of the Timeform system, John Randall and Tony Morris rated Sun Castle an "average" winner of the St Leger.