He showed up on Long Island in the summer of 1919 with a polo mallet in one hand and a business card reading, “George Gordon Moore, Capitalist,” in the other. London had been his financial playground before the war, but the war had bled England dry.

Forty-five at the time, Moore knew there was wealth to be mined on Long Island’s North Shore. With its country estates and pristine oceanfront, it was a paradise for socialites, celebrities, and well-heeled entrepreneurs in search of glamour and the good life. Long Island was one of those places, as F. Scott Fitzgerald wrote in The Great Gatsby, where “people played polo and were rich together.” And that’s where Moore—my grandfather, and a likely model for Fitzgerald’s hero—met the man who would become the novel’s antagonist, Tom Buchanan.

Moore had come from California as captain of the Santa Barbara Polo Club team with the ambition to dominate the East Coast’s summer polo season. The California team appeared, according to one writer, like “a band of outlaws let loose in the manicured gardens of the East.” Among their most formidable opponents was the long-established Meadow Brook team, of Old Westbury, Long Island, whose secret weapon was Tommy Hitchcock, a celebrated young war hero who had just completed his first semester at Harvard.

Tommy Hitchcock, believed to have inspired Fitzgerald’s antagonist Tom Buchanan.

Hitchcock was an extraordinary athlete, combining bravery, cunning, and ruthlessness with grace and humility that gained the respect of every player he faced. Fans and sportswriters idolized him on and off the field.

Long Island was one of those places, as F. Scott Fitzgerald wrote in The Great Gatsby, where “people played polo and were rich together.”

A high point of the 1919 season was the Monmouth Cup championship, in Rumson, New Jersey, which pitted Meadow Brook against the Santa Barbara team. From the moment the players rode onto the field—Meadow Brook in their trademark robin’s-egg blue and the Santa Barbara players in their all-white jerseys—it was clear that the game would be an epic confrontation between the blue-blooded civility of the East and the red-blooded barbarism of the West.

George Gordon Moore, left, and Hitchcock, second from right, after a polo match.

The competition was ferocious, and Moore was the most ferocious of all. He repeatedly blocked Hitchcock by digging his shoulder into Hitchcock’s ribs. At one point, when Hitchcock tried to gallop past him, Moore shouted, “You son of a bitch!,” and struck him, accidentally or otherwise, on the side of the head with his mallet. A few strides later, Hitchcock realized that the blow had lacerated his ear. He left the game long enough to be bandaged up, and came back onto the field determined to show the older player that he could play just as rough.

Santa Barbara defeated Meadow Brook that day. Hitchcock never liked to lose, but he was impressed by Moore’s ruthless tenacity. Moore likewise admired Hitchcock’s unflinching mastery of the sport and his effortless upper-class gentility. Despite their 25-year age difference, the two competitors became close friends.

Like so many other young men who had survived the war that Fitzgerald called “that delayed Teutonic migration,” Hitchcock had returned home feeling aimless and confused. The thrill and danger of battle had exhilarated him, and he sought to replicate the experience on the polo field. While some found Moore’s brutality offensive, Hitchcock relished it.

Players at the Meadow Brook Polo Club, on Long Island, in 1939.

Moore had also experienced the war firsthand, as a close friend and adviser to Sir John French, commander in chief of the British forces in the early phases of the conflict. His latest gambit involved mining metals, an exotic pursuit that sparked Hitchcock’s sense of adventure.

Imagining a future for himself in Moore’s rugged realm of business, Hitchcock studied chemistry at Harvard. After his graduation, in 1922, Moore took him on as his professional protégé. That fall, Hitchcock began working at Moore’s office, in Midtown Manhattan, learning the intricacies of the minerals trade, speculation, and finance. They shared a town house that became legendary for its extravagant, champagne-soaked parties attended by journalists such as Arthur Krock and fashionable writers including Padraic and Mary Colum.

At the same time that Hitchcock was settling into his new life in Manhattan, Fitzgerald was settling down in the Long Island town of Great Neck. One of the first people he met was Tommy Hitchcock. Fitzgerald instantly idolized Hitchcock; like Moore, he admired Hitchcock’s patrician ease and peerless athleticism. But those same qualities also drew Fitzgerald’s resentment. When he sat down to write The Great Gatsby, he modeled Tom Buchanan, Daisy’s well-bred, brutish polo-playing husband, on the young polo star.

Given Hitchcock’s intimate connection with Moore at the time, it’s hard to imagine that Moore and Fitzgerald did not cross paths. Indeed, they most likely met at one of Moore’s celebrated soirées.

The close relationship between Moore and Hitchcock epitomized the collision of old and new money that was to define the Roaring Twenties. Hitchcock was the soul of aristocratic propriety; Moore was a man of the frontier who did not always follow the playbook of the ruling class. From their partnership grew the “romantic readiness” that Fitzgerald instilled in his immortal hero, Jay Gatsby.

Bruce Dern, Lois Chiles, Mia Farrow, and Robert Redford in the 1974 film adaptation of The Great Gatsby.

It seems likely that Gatsby was a composite of several people Fitzgerald knew or knew about, but it’s hard to ignore Moore as a top candidate. The economic historian Charles R. Morris noted that Moore had “entered international society by staging Gatsby-like bacchanals on his Long Island estate and in London” and suggested that Gatsby’s “wild parties” may have been modeled after Moore’s. Hitchcock’s biographer, Nelson W. Aldrich Jr., wrote that Moore “might have sat for the portrait of Jay Gatsby.”

Of course, as his granddaughter, I’m not exactly a neutral party. Yet, however you cut it, polo, parties, and the hapless pursuit of the American Dream—all the elements were there for Fitzgerald to spin into his masterpiece, The Great Gatsby.

Mickey Rathbun is an Amherst-based writer whose work has appeared in the Chicago Tribune, The Boston Globe, and elsewhere