Warning was scheduled to end his season by meeting another unbeaten colt, Reprimand, in the Group One Dewhurst Stakes at Newmarket in October, but was withdrawn from the race as Harwood felt he would be unsuited by the soft ground.

Warning was the early favourite for the 2000 Guineas[6] but in his prep race he was beaten four lengths by Doyoun in the Craven Stakes at Newmarket.

Warning did not appear until July when he ran in the Bet With The Tote Trophy, a Listed race over one mile at Lingfield Park.

In the Queen Elizabeth II Stakes at Ascot Racecourse on 24 September, Warning started 9/4 joint-favourite with Soviet Star, who had defeated Miesque in the Prix du Moulin.

Warning turned into the straight in sixth place but accelerated to take the lead a furlong from the finish and drew clear of the field to win "very easily"[10] by five lengths.

At Royal Ascot in June he appeared to recover his best form in the Queen Anne Stakes, taking the lead approaching the final furlong and accelerating clear to win by four lengths from Reprimand.

He started second favourite but tired badly in the closing stages[12] and finished fourth behind Nashwan, Opening Verse and Indian Skimmer.

[13] In 1987 Warning was the top-rated two-year-old colt in Europe's official International Classification with a rating of 125, placing him equal with the filly Ravinella.

[14] In their book A Century of Champions, based on a modified version of the Timeform system, John Randall and Tony Morris rated Warning the best British-trained racehorse of his generation.

[16] Pat Eddery described Warning as "a brilliant horse" and an "absolutely top miler" adding that he was "a lovely little fellow, not very big but a gentleman".