How does Big Red win the race in Kenilworth Park against Sir Barton in the novel, King of the Wind?

Big Red wins the race in Kenilworth Park by using his natural ability for speed. Sir Barton, a natural sprinter, races past Big Red at the beginning of the race. Although Big Red's jockey originally wants to hold Big Red back and preserve his mount's speed for the end of the race, he notices that Big Red wants to move faster. Remembering the trainer's advice, the jockey allows Big Red to run as fast as he wants. Big Red surprises the audience by darting past Sir Barton and maintaining his speed to win the race.