In one split second, Phillip Dutton held the left rein tight, shifted his body weight and glanced down to see if his mid-air reaction had pushed Mighty Nice inside the red flag.

Approaching the sixth fence of a grueling cross-country course at the 2016 Olympic Games in Rio de Janeiro, “Happy,” on his last stride, caught sight of the back of a corner brush jump and, momentarily confused, drifted hard to the right.