What's the reason behind the cursed distance of a marathon? The mythical explanation is that, around 490 BCE, the courier Pheidippides ran from Marathon to Athens to deliver news that the Greeks had trounced the Persians at the Battle of Marathon. The trouble with that explanation, however, is that Pheidippides would have only covered a distance of approximately 25 miles. So what accounts for the extra 1.2 miles?

When the modern marathon appeared in the late 19th century, the race distance was inconsistent. During the first Olympic games in 1896, runners jogged along Pheidippides’s old route for a distance of 40,000 meters—or 24.85 miles. (That race, by the way, was won by a Greek postal worker.) The next Olympic games saw the distance bumped to a pinch over 25 miles. And while subsequent marathons floated around the 25 mile mark, no standard distance was ever codified.

Then the Olympics came to London. In 1908, the marathon, which stretched between Windsor Castle and White City Stadium in London, lasted 26.2 miles—all for the benefit of England's royal family.

It wasn't supposed to be that way. Like previous races, the original event was supposed to cover a ballpark of 25 miles. The royal family, however, had other plans: They wanted the event to start directly in front of Windsor Castle—as the story goes, the royal children wanted to see the start of the race from the castle nursery. Officials duly agreed and moved the starting line, tacking on an extra mile to the race.

As for the pesky final 0.2? That was the royal family’s fault, too. The finish line was extended an extra 385 yards so the race would end in front of the royal family’s viewing box.

Those extra 1.2 miles proved to be a curse. The race’s leader, an Italian pastry chef named Dorando Pietri, collapsed multiple times while running toward the finish line and had to be helped to his feet. One of the people who came to his aid was a journalist named Arthur Conan Doyle. Afterward, Conan Doyle wrote about Pietri's late-race struggles for the Daily Mail, saying, "Through the doorway crawled a little, exhausted man ... He trotted for a few exhausted yards like a man galvanized into life; then the trot expired into a slow crawl, so slow that the officials could scarcely walk slow enough to keep beside him."

After the London Olympics, the distance of most marathons continued to hover between 24 and 26 miles, but it seems that Conan Doyle's writing may have brought special attention to the distance of 26.2, endowing it with a legendary "breaker-of-men" reputation. Indeed, when the International Amateur Athletic Federation convened to standardize the marathon, they chose the old London distance of 26 miles and 385 yards—or 26.219 miles.

Writing for Reuters, Steven Downes concluded that, "the marathon race may have been as much a Conan Doyle creation as Sherlock Holmes."

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