His success in the last race, in which he decisively defeated the British champion Airborne provoked widespread debate in Europe concerning the superiority of French horses in long-distance events.
[5] Souverain recorded his first important success when he won the three-year-old version of the Prix Jean Prat over 2000 metres at Longchamp Racecourse in April.
In October, Souverain recorded another important success when he defeated Prince Chevalier in "storming fashion"[2] in the Prix Royal Oak, the French equivalent of Britain's St Leger Stakes.
[8] Ridden as usual by Lollierou, Souverain "shot clear" of the field in the straight and won easily by five lengths from Bright News, with Airborne, the favourite, in third.
Among the theories advanced to explain his win was the supposedly unlimited supply of milk and German oats provided to French horses at the end of the Second World War.
[5] Lord Brabazon, writing in Nature blamed bad tactics by British jockeys who tended to restrain their mounts before accelerating in the closing stages and was supported by the physiologist Archibald Hill who argued that horses performed better when they ran at a uniform speed.
[10] French experts however, pointed to the tendency of British breeders to undervalue stamina in pedigrees and place undue emphasis on sprinting and two-year-old races.
[4] Later that month he ran in the 4000 metre Prix du Cadran but was decisively beaten by the seven-year-old Marsyas who was winning the race for the fourth time.