In 1914, Rees enlisted as a private in the Sussex Yeomanry, was commissioned into the Manchester Regiment and ultimately seconded to the Royal Flying Corps as an observer.
[4] Rees resumed his National Hunt career after his demobilisation from the Army, turning professional in January 1920 to ride for Lewes-based trainer George Poole.
[8][10] Rees' most significant winning rides were spread across this period of sustained success, with arguably the most famous coming early, in the 1921 Grand National at Aintree in Liverpool.
At the penultimate fence The Bore dismounted his jockey, Harry Brown, and Rees found himself sufficiently free of the pack to bring Shaun Spadah home in comfort, scoring victory by a distance.
On the final flat, Red Splash was left to fight it out with Conjuror II and ultimately came home to win by a head.
[16] Rees won the Cheltenham Gold Cup for a second time in 1928 on his mount Patron Saint, a Welsh-trained horse from the stables of Stanley Harrison, owned by F. W. Keen, priced at 7/2.
[17] Patron Saint spent much of the race behind favourite Koko, but pulled ahead on the rails in the turn before the final straight.
[19] Rees was back in the saddle within the hour as he attempted to become the first jockey to win back-to-back runnings of the Cheltenham Gold Cup.
Establishing an immediately lead from the off, comfortably clearing each fence as it came, Rees bought his horse home in a canter by 20 lengths.
[21] By the early 1930s Rees, who had suffered a number of injuries in the saddle (including a broken leg in 1927)[22] was struggling to maintain his conditioned weight.
[1] in accordance with Rees’ own wishes, his ashes were sprinkled on the grave of his 1921 Grand National winning horse, Shaun Spadah, at Lewes racecourse, who had been buried there on his death in 1940.