He showed good form as a three-year-old, winning the Queen's Vase and finishing second in the classic St Leger Stakes, but reached his peak as an older horse.

He won the same three races as a five-year-old, defeating the future champion Ardross on each occasion, and in doing so becoming the only horse ever (or since) to win the "Stayers' Triple Crown" twice.

He established himself as one of the leading stayers of his generation at Royal Ascot in June when he was ridden by Geoff Baxter to win the Queen's Vase over two miles at odds of 7/4.

The following month, again ridden by Baxter, he defeated the mighty Sea Pigeon in the valuable Tennent Trophy over one mile and seven furlongs at Ayr.

Ridden by Joe Mercer, he led from the start and repelled the persistent challenge of the Irish-trained four-year-old Ardross to win by three-quarters of a length.

In a repeat of their Ascot clash, Le Moss and Ardross dominated the closing stages of the race, with the older horse winning by a neck.

Mercer blamed himself for the defeat, admitting afterwards that he did not set a strong enough gallop and thereby placing more of an emphasis on stamina, his mount's greatest attribute.

[9] They described him in their annual as "a powerful, relentless galloper......a phenomenon among racehorses: he's not the best long-distance horse we've ever seen, but if there is such a thing as a top-class racehorse that stays forever, Le Moss is probably the closest to him we have encountered since that great out-and-out stayer of the mid-forties Marsyas II, and on the score of determination and courage, precious few stayers of the post-war era rank with Le Moss......His performance in winning his second Gold Cup was one of the most stirring seen on a racecourse in many a year; it was an unforgettable display of endurance and courage......When he took the so-called stayers triple crown as a four-year-old he became the first horse to do so for over twenty-five years, and no other horse has completed that notable treble two years in a row.

And he achieved his second treble the hard way, making virtually every yard of the running in almost seven and a half miles of competition......In terms of merit, we rate Le Moss (135) higher than his famous brother Levmoss (133).

Although he had raced throughout 1980 in the colours of Carlo d'Alessio, he was bought after the Ascot Gold Cup by Paddy McGrath (a trustee of the McGrath Trust Company, his breeders) for a reported £250,000 and leased back to d'Alessio for the remainder of his racing career before taking up stallion duties in 1981 at Brownstown Stud, the place of his birth.