Natroun over 2400 metres at Longchamp Racecourse on 7 May. Two weeks later he contested the Prix de l'Avre over the same course and distance and won by five lengths from Bilal. Following the race, the colt's owner paid a supplementary entry fee of approximately £15,200 to enter the horse in the Prix du Jockey-Club, reportedly at the urging of Saint-Martin. On 7 June, Natroun contested the 150th running of the Prix du Jockey-Club over 2400 metres at Chantilly Racecourse. In France, horses in the same ownership or stable are coupled for betting purposes. The Vincent O'Brien pair Ancient Times and
Prix du Jockey Club Club was staged at Longchamp in 1941 and 1942, and at Le Tremblay over 2,300 metres in 1943 and 1944. It returned to Longchamp for the following three years, and on the second occasion it was opened to foreign participants. The present system of race grading was introduced in 1971, and the Prix du Jockey Club was classed at the highest level, Group 1. The first foreign-trained horse to win was Assert in 1982. The distance was shortened to 2,100 metres in 2005. Nine winners of the Prix du Jockey Club have subsequently won the Prix de l'Arc de Triomphe.