[3] The colt was sent into training with Bruce Hobbs at his Palace House stables in Newmarket and was ridden in his British races by the lightweight jockey John "Kipper" Lynch.
He appeared to be less than fully fit, but showed some promise to finish third, beaten two lengths and a neck by Indian Brave and Sandford Boy.
Tromos raced close to the lead before going clear of the field in the last quarter mile and drawing away to win by thirteen lengths from the Queen's colt Milford.
[5] In October, Tromos was moved up in class and distance to contest the Group One Dewhurst Stakes, Britain's most prestigious race for two-year-olds over seven furlongs at Newmarket Racecourse.
[5] Tromos began his three-year-old season at Newmarket in April when he started 30/100 favourite for the Craven Stakes, a trial race for the 2000 Guineas.
Tromos fought his jockey's attempts to hold him up and in the closing stages he never looked likely to catch the front-running Lyphard's Wish and finished second, beaten two and a half lengths.
[9] In 1978 the independent Timeform organisation gave Tromos a rating of 134, making him their highest-rated two-year-old of the season, two pounds ahead of the French-trained filly Sigy.
[10] In the inaugural International Classification, a collaboration between the official handicappers of France, Ireland and the United Kingdom, Tromos was rated the best two-year-old in Europe ahead of Sigy and Irish River.