Hidden among the cow pastures and rolling meadows of Somerset, in the Southwest of England, Middlemoor Water Park features a muddy man-made waterskiing pond, a go-kart track, and a shack selling beer and snacks. But on November 24, 2002, Middlemoor’s main attraction was somewhat more exotic: in a clearing behind the gravel parking lot stood a replica of a trebuchet—a medieval catapult—looming like an oil derrick against the sky. Twenty-six feet tall at rest, made of steel and rough timber, the trebuchet was, according to its builder, a onetime motorcycle salesman and scrapyard owner named David Aitkenhead, “a big, evil, savage-looking contraption.” On this day, the machine was being prepared to violently hurl willing human beings several stories high and into a net 100 feet away.

It was a warm day and a crowd of at least 30 had gathered to watch the trebuchet in action. Most were Oxford University student members of the Oxford Stunt Factory, a private alternative- and extreme-sports club. They had arrived in a caravan organized by the head of the club, David “Ding” Boston. The majority had come as spectators. A handful, however—including an enthusiastic 19-year-old freshman biochemistry student from Bulgaria named Kostadine “Dino” Iliev Yankov—were intent on taking a turn.

The proceedings got rolling as the first daredevil was placed in the trebuchet’s sling and then flung in a perfect, arcing parabola into the center of the net, which sat atop 26 stout telegraph poles on the other side of the clearing. Four more successful throws followed. “There was a half-hour between jumps,” remembers Boston, who was videotaping the event from a position beyond the landing area. “It was really a question of keeping yourself busy as they adjusted the weights.”

Finally, it was Yankov’s turn. “I was looking through the video lens,” says Boston, “and I saw the same thing I had seen on the previous throws except that, the moment when I expected him to come into the viewfinder, there was nothing. And then, milliseconds later, a very dull, heavy thud.”

Yankov’s body had missed the net by inches and come crashing to the earth, where he now lay in a broken heap. “You expected to see one of the bearings broken, or a wheel rolling away, or the net hanging, or something,” Boston says. “But there was just Dino, on the ground, making the most ghastly, guttural sounds.”

A helicopter arrived and rushed Yankov to a hospital in Bristol. But the catapult had sent him on a trajectory equivalent to being thrown over a house. By 7:30 P.M. he was dead. Aitkenhead and his partner, Richard Wicks, were arrested eight days later and were eventually charged with manslaughter. Their trial will take place sometime this year.

The sad story made a few headlines in the English papers and would likely have died as a three-line item in “news of the weird” blogs around the world if it hadn’t been for the fact that Aitkenhead and Boston share a distinguished pedigree. Both men served time in the Dangerous Sports Club, a gathering of brilliant and adventurous souls that came together in Oxford in the late 70s and, in a burst of imagination, mischief, and style, more or less invented the world of alternative sports. In the decade when it burned brightest, the D.S.C. pioneered hang gliding, invented bungee jumping, sent a grand piano down the slopes at Saint-Moritz, Switzerland, and generally raised a good deal of witty, iconoclastic hell on several continents before going the way of all things that start out new and exciting and then inevitably run their course. The trebuchet accident was a tragic coda to this history, though exactly when—and if—the saga of the D.S.C. came to an end is among the most contentious questions of all.