Mill Reef
Balding was trainer of the winning horse, Mill Reef (1968–1986), ridden by Geoff Lewis, in the 1971 The Derby Stakes or Epsom Derby. The winning time was recorded at 2:37.14. Balding was again Mill Reef's trainer when the horse won the 1971 Prix de l'Arc de Triomphe at Longchamp Racecourse in Paris, France. Philanthropist Paul Mellon was Mill Reef's owner and the horse was again ridden by jockey Geoff Lewis. The purse won was €1,600,000. Mill Reef was introduced to racing older horses at Sandown Park in the Eclipse Stakes. With the same owner and jockey Mill Reef came in at a time of 2:05.40. 1971 was an excellent year for this three-year-old horse and its team, coming in first at the King George VI and Queen Elizabeth Stakes with a time of 2:32.56 on the 1 mile 4 furlongs (2,414 m) Ascot Racecourse. Even though Mill Reef was born and bred at the Virginia Rokeby Stables he was sent to England to race on turf courses in Europe and to be trained by Balding. Geoff Lewis rode Mill Reef in all his races, bearing the owner's colours: black with gold cross, stripe on cap.