How it unfolded
Zatopek had already won the 10000m and 5000m at these Games, both in Olympic-record times. He had never once finished a marathon in his life, but decided mid-Games to enter anyway. Early on he tucked in beside Britain's Jim Peters, then the world's best marathoner. At the 15km mark Zatopek asked whether the pace was fast enough; Peters, joking, said it was too slow. Zatopek took the remark literally and lifted the pace, and Peters cramped and dropped out near the 30km mark. Zatopek ran the rest alone and entered the stadium in an Olympic-record 2:23:03.2, more than two and a half minutes ahead of Argentina's Reinaldo Gorno in second. He caught his breath at the finish and waited for the other runners to come in. No one, before or since, has won the 5000m, 10000m and marathon at a single Games.
Why it still matters
This redefined the very range a distance runner could cover. The idea that track speed and marathon endurance were incompatible collapsed within two weeks, and the massed interval training Zatopek pioneered while running in army boots became the worldwide standard for distance training. His Helsinki triple remains the only one of its kind to this day.