The boxer and his boyfriend sat together on a train hurtling along the New York subway. Emile Griffith had pulled a hat down over his eyes. He was not in the mood to make eye contact with anyone just before the Saturday morning weigh-in for his world title fight that night, 24 March 1962, at Madison Square Garden. It would be the third time he’d face his bitter rival Benny “Kid” Paret – in a career which would eventually see him become one of the finest welterweight champions in history.

Griffith went on to fight 337 world championship rounds – 69 more than Muhammad Ali. But his place in the pantheon would be darkened forever by his tragic trilogy against Paret.

Photograph: Simon & Schuster

He had lost his world title to Paret seven months previously. The Cuban had upset Griffith at the weigh-in to that bout by taunting him as a maricón [“faggot”.] In boxing’s macho world there could be no greater insult – especially when it was an open secret that Griffith was “different”. It was not just that he spoke of his pleasure in designing pretty bonnets for ladies or could discuss the latest pillbox hat worn by Jackie Kennedy outside the White House.

Emile Griffith was gay at a time when homosexuality was derided as a disease, condemned as a sin and classified as a crime. Even consensual sex between two adult men could result in their imprisonment. Homosexuality was a criminal act in every state of America – apart from Illinois. The American Medical Association, meanwhile, persisted in classifying homosexuality as a “psychiatric disorder”.

The renowned fighter visited gay bars most weekends – but he found it impossible to come out with a public statement about his sexual preference. It was imperative to bury the truth because a gay boxer was an unimaginable phrase. In the early 1960s the subject was not only taboo; it was impossible to believe that any sporting hero, a man’s man, could be a homosexual.

Emile didn’t like thinking about it much. He was just happy belonging to two contrasting groups of men, whether he was fighting them or loving them.

He left the subway at 42nd Street. Before battle he wanted the comfort of walking along the familiar streets of Times Square where, at night, he laughed and danced with the Hispanic gay crowd and the old drag queens. Just before 11 am that Saturday morning, and on the day of the biggest fight of his life, men, women, transvestites, hookers and strippers called out to wish him good luck. Normally, he would stop and talk to everyone. But, then, Emile just raised his fist to his people and walked on. He would be fighting for them too.

Benny Paret laughs as he reads the weight of challenger Emile Griffith during weigh-in at the Garden in New York, the scene of their fateful fight. Photograph: John Lindsay/AP

At the weigh-in, Paret was in a party mood. But Griffith looked like he was undressing for a funeral. In his underwear, he stepped on to the giant scales. The Kid pointed at the marker and laughed. He could not believe Griffith had come in as light as a fairy – at 144 pounds.

Griffith was about to step off the scales when he heard his trainer Gil Clancy shout: “Hey, watch it!” He wheeled round. A smirking Paret feigned intercourse with him as his trainers whooped hysterically. He waggled a finger at Griffith. “Hey maricón,” Paret said in a cooing lisp, “I’m gonna get you and your husband.”

If a white fighter had sneered at the colour of his skin Emile would have shrugged it off. But the onslaught against homosexuality ran deep and wide. A homosexual, in 1962, was ridiculed as being sick and cowardly. It did not matter that, in the case of Emile, he was trying to become just one of eight men on earth to call himself a world champion at a time when boxing held profound meaning in America.

Emile, in private, was proud that he could fall for a man. In public, he felt ashamed and angry that his secret life was being demeaned. How could Paret be so cruel? He was about to hit Paret harder than he had hit anyone before when Clancy dived between the fighters. “Save it for tonight, Emile,” he hissed.

Benny Paret went back to the Bronx. All the mischief of the weigh-in had drained out of him. He felt lonely. Benny wished his wife Lucy had come with him to New York. He remembered how, just four days before he left for his camp, Lucy had held him when he’d cried. They had taken little Benny Jr to the zoo in Miami but, at the entrance, they’d been turned away.

“You’re coloured,” Benny had been told.

Lucy had been stunned when her husband, rather than their small son, had shed tears. The injustice reminded Benny that, rather than being a world champion, he still looked like a Cuban sugarcane cutter.

Benny had tried unsuccessfully to persuade her to leave Miami with him so she could watch him retain his title. But for weeks, even though she had not told him, Lucy had dreamed terrifying dreams of Benny being hurt. She could not shake the images from her head.

Emile Griffith trains for Madison Square clash with Joey Archer. Guardian

He normally never said much – but when Benny telephoned Lucy from the Bronx the words spilled out of him like blood from a gash. His head hurt and he did not want to fight. Lucy pleaded with him to withdraw from the contest; but Benny knew his manager, Manuel Alfaro, would never allow it. There was too much money riding on the fight. He said goodbye softly, and the line went dead.

At ringside, alongside the cigar-wielding gangsters and bent politicians, the fight writers were still absorbing the shocking weigh-in. They could hardly believe Paret had acted so graphically – or that Griffith had reacted with such raw pain.

It had been hard for them to know how to write about the incident for their early evening editions but Howard M Tuckner, of the New York Times, tried his best. He had written sensitively about the weigh-in, aware that homosexuality spelt out forbidden territory on the sports pages. Maricón was the deadliest insult in Hispanic culture; but Tuckner was also aware that they lived in a society where Liberace was still allowed to pretend that he was a straight man. Tuckner, like everyone else on the boxing beat, realised that Griffith was a homosexual. But that did not impinge on his decency as a man and his ferocity as a fighter.

Out of respect to Griffith, and a conservative world, Tuckner reported soberly that the challenger had been subjected to a slur about his sexuality.

Just before 9pm, while ringside at Madison Square Garden, Tuckner collared young Pete Hamill and raged against the totalitarian idiots on the copy desk at the New York Times. Hamill worked for the New York Post, a tabloid, but Tuckner had made it to the peak of his profession and the supposedly magisterial sports desk of the Times. Tuckner was incandescent.

The Times subeditors had replaced the offensive word of “homosexual” with the meaningless phrase “un-man”. Tuckner could not believe it when, on his way to the fight, he had picked up the paper and, under his byline, read that Paret had accused Griffith of being an “un-man”.

Tuckner shouted out his disbelief to Hamill. “Un-man?” he yelled. “What the fuck is an un-man? A butterfly is an un-man. A rock is an un-man …”

Knocked unconscious by a lethal barrage of blows, the defeated champion Paret sags on the ropes as referee Goldstein keeps a tight hold on Emile Griffith. Photograph: Corbis

He was still yelling when the lights dimmed in the Garden. A visceral roar echoed around the arena. The battle between the macho Cuban sugarcane refugee and the hat-making “un-man” was about to begin.

That night, rage and hurt poured out of Emile Griffith. It was a savage fight and, even though he was knocked down in the sixth round, Griffith dominated. Carnage broke out in round 12. It started with two brutal right hands from Griffith. Paret teetered backwards. He buckled sadly towards oblivion.

In that moment, Griffith might have allowed the champion to fall. But he was about to punish Paret. The Cuban tried to hold his guard up but his arms were too weak. Griffith had a clear target of Paret’s lolling head. He used his left arm to pin Paret against the ropes while he threw a sawing right uppercut again and again. Griffith turned his body so that he could gain maximum torque with every punch he threw. Each one landed with deadening force. Paret’s head rocked on a neck that looked like a broken plinth.

One punch followed another in a shocking cortege. It was as if each blow was in answer to the taunt of maricón.

The blows were so savage that the referee, Ruby Goldstein, seemed helpless, as if the ferocity had struck him dumb. At ringside they could hear the sound of every punch as if it was the distant echo of a heavy spade digging a grave.

After a dozen right uppercuts, Griffith suddenly threw the left hand. The sight of two fists, drilling like pistons into Paret’s defenceless head, finally snapped Goldstein out of his stunned reverie. He jumped between the fighters.

The only way he could stop Griffith hitting Paret was by wrapping his arms around a man who had been deformed into a punching machine. As Goldstein and Griffith staggered away in a drunken embrace, Paret slid down. His eyes began to close as he started to die. Paret’s right arm was trapped against the ropes, while his left spread out in a surreal crucifixion.

At ringside, Gaspar Ortega, who had fought both men, was distraught. The way in which Paret had slipped away, as if he had already left his limp body, frightened Ortega. He began to cry as, reaching for his wife’s hand, he pulled her away. They needed to escape the Garden.

A few minutes later, in the middle of the ring, the television commentator Don Dunphy had not understood the outcome as completely. “Here is Emile Griffith, the young man who has regained the world welterweight championship in an exciting fight with Benny ‘Kid’ Paret. Emile … we’re going to replay the knockout in slow-motion videotape. I’d like you to describe what happened.”

Onlookers line the streets in New York to watch the funeral procession of Paret, who died as a result of injuries sustained during the fight with Griffith. Photograph: Bettmann/Corbis

Emile hesitated, as he saw himself beating the life out of Benny Paret on a black-and-white monitor.

“He’s hurt now, see,” Dunphy said, encouraging Emile to look more closely. “That’s beautiful camerawork there.”

“Yeah, terrific,” another voice confirmed. It was the first time in television history that a slow-motion replay had been used.

They fell silent as they watched. But Dunphy, knowing that dead-air on television was a crime, eventually chipped in: “There it is,” he said.

“I just kept punching,” Emile said, horror thickening his voice. “I just kept punching …”