For six months, Princess Bride star Mandy Patinkin had trained to become Inigo Montoya, the world’s greatest swordsman. His worthy opponent, the Man in Black/Westley—played by Cary Elwes—had four months of prep under his belt as well. Spirits were high as the actors performed their duel for director Rob Reiner on the Cliffs of Insanity set for the first time, in London in 1986.

Elwes and Patinkin finished, drawing applause from the film’s crew. Then, both drenched in sweat, they looked to Reiner, who voiced his own response: “That’s it?” It wasn’t exactly the reaction they had hoped for.

“What’s lovely about Rob is he’s nothing if not direct,” Elwes tells Vanity Fair, 30 years after The Princess Bride hit theaters nationwide. “That’s why he’s so wonderful—what you see is what you get.”

As it turns out, the actors had become a little too good at sword fighting. The duel that they had rehearsed for months was over much more quickly than Reiner expected.

“They had certainly mastered the moves,” Reiner says. “But I said, ‘We’ve got to make this more epic. It has to be longer, and it has to use all the parts of the set.’” So the scene’s stars, trainers, and crew went back to the proverbial drawing board.

In older movies, duel scenes featured movie stars in close-ups only; the rest was done by stuntmen. But Reiner bucked that tradition, insisting that Elwes and Patinkin do all the swordplay themselves.

The two were up for the task—especially Patinkin. Then in his mid-30s, he had learned to fence more than 10 years earlier at Juilliard. But before traveling to London to shoot The Princess Bride, he spent two months working with Henry Harutunian, the head coach of fencing at Yale.

“We’d work 8 to 10 hours a day,” says Patinkin. Harutunian taught him basic steps and—in order to prepare the actor for the scene’s big reveal—initially made the right-handed Patinkin train using only his left hand. Twenty-four-year-old Elwes, by contrast, figured training would begin once shooting did. “I had no fencing training at all, so I was very much behind,” he says.

Upon arrival in London, both actors worked with the best: legendary British stuntmen Peter Diamond and Bob Anderson. Diamond is best known for sword-training Errol Flynn and Burt Lancaster, and as the stunt coordinator/arranger for films such as the original Star Wars trilogy, Raiders of the Lost Ark, and Highlander. An Olympic fencer for Great Britain and a trainer, Anderson was also the double for David Prowse (who played Darth Vader) during the lightsaber duels in The Empire Strikes Back and Return of the Jedi.