A picture taken February 25, 1964, in Miami, during the match at the end of which the American Cassius Clay (Muhammad Ali) became world heavyweight boxing champion against his compatriot Sonny Liston.

Fifty years ago, the world woke to the Muhammad Ali legend, writes Jeff Powell.

London - It is 50 years since a boxing match changed the course of history. Half a century from the night a brash kid named Cassius Clay beat a terrifying brute of a man called Sonny Liston for the world heavyweight title – and in so doing challenged America to confront its own dark reality.

“I shook up the world,” Clay famously screamed.

More than he knew at that frenzied moment when Liston failed to answer the bell for the start of the seventh round.

“I’m the Greatest,” the Louisville Lip shouted above the pandemonium in the Convention Hall at Miami Beach. On that evening of February 25, 1964, we all assumed that this seemingly demented being was alluding solely to his prowess at prize-fighting.

He had indeed rocked planet Earth with one of the most seismic sporting upsets of all time. And, yes, the dazzling manner in which he did so excited predictions a legend really had been born. Yet the world was soon to discover this was not even the half of it.

The following day, Clay announced he was changing his name to Cassius X.

Within a week, he declared he was rejecting his “slave name” entirely, demanded he be known thereafter as Muhammad Ali and pronounced himself a member of the Black Muslims.

That public affiliation to what was perceived as a “hate-white” group was to have repercussions that grew with his fame and would alter the landscape of US life.

A suspicion that he had already joined the Nation of Islam before the fight so disturbed white America that many shied away on the night and the promoter of one of the most significant sports events ever staged ended up out of pocket to the tune of $300 000.

That turned out to be the price of providing a global platform for the man whose rocketing stardom was to make him the noisiest and most visible spokesman for the civil rights movement.

The American majority would spend decades trying to deny Ali’s phenomenal talent to discredit his message. But not even the furore that surrounded his refusal to be drafted for military service in the Vietnam War – and his resulting three-year banishment from the ring – could silence that brilliant voice.

It has taken Parkinson’s disease to do that – but not before his own country had joined the rest of the world in acknowledging that he is indeed The Greatest of all time. Before any of that, however, he first had to defeat a man regarded as a monster. Liston was nicknamed “Big Bear”; Clay called him the “Big Ugly Bear”.

The goading went on for weeks and many thought Clay, in his 22-year-old craziness, was signing his own death warrant.

Clay insisted it was Liston who would be killed and that he would then use his hide as a bearskin rug in his living room. One morning he turned up on the doorstep of Liston’s home to screech that threat.

At the weigh-in, Clay sported a denim jacket emblazoned with the logo “Bear Huntin’” and worked himself into such a lather that his heart rate soared from below 60 beats a minute to above 120.

Mind games on an epic scale or plain fear? Both.

Of the stare-down before the first bell, Clay was to admit later: “I won’t lie. I was scared just knowing how hard he hit. But I didn’t have no choice but to go out and fight.”

Clay knew Liston was older than the 32 years he claimed – more like 40 – and that the ominous presence and fearsome criminal reputation hid an insecure man so simple as to be almost childlike.

If Liston was bemused by Clay’s antics before the fight, he became totally befuddled as soon as it began. The first-round charge with which he expected to blow this upstart away hit… thin air.

Not only did Clay dance away, but as he did so he clipped the fighter thought to be invincible with lightning combinations.

A desperate Liston caught Clay with a huge left in the second, but neither he nor the rest of us were as yet aware that this kid had the chin of a buffalo.

Clay took full control in the third, in which Liston suffered a cut eye for the first time in his career and which he ended gasping for air.

When Clay got back to his corner, he complained his eyes were on fire and begged for his gloves to be cut off. The blame was laid on a substance used to treat Liston’s cut. Clay’s fabled trainer, Angelo Dundee, sponged down his face and told him “get out there and run”.

So reluctantly did he comply that he was almost disqualified for delaying the start of the fifth. He stayed out of trouble, despite shouting: “All I can see of that bear is a shadow.”

His vision cleared, fatefully for Liston, as he spent the sixth being pummelled by clusters of punches too fast for him to comprehend. At the round’s end he slumped, bewildered, on his stool and refused to rise again. The vacant expression told its own story of a mental blockage.

Clay went on to become Ali. The Greatest. The fighter for freedom as well as world titles. The most recognisable person on the planet.

Liston died alone in his bathroom on December 30, 1970, his heart as broken as his mind.

Ali, at 72, lives on. Which, after all these years in the clutches of Parkinson’s, is another remarkable tribute to his fighting spirit.

The “big ugly bear” he taunted is buried in a cemetery below the flight path at Las Vegas airport, his tombstone simply inscribed with these two words: A Man.

Whenever Ali travels to Sin City, he visits that grave. After all, without Charles “Sonny” Liston, Cassius Marcellus Clay could not have shaken up the world.