After 14 rounds of unremitting brutality and with the two heavyweights on the verge of collapse, Frazier's corner told their man it was time to quit.

Frazier's left eye was closed, he could barely see out of his right and nothing he was likely to produce in the final round was going to change the result.

Ali, slumped in his corner and drenched in sweat, had won the third and most brutal fight against an opponent who forced him to draw on resources his detractors believed he did not possess.

A year after he astonished the world by vanquishing the fearsome George Foreman, Ali was again king, indisputably the greatest of his era and possibly of all time.

Victory in the 'Thriller in Manila' came with a literally crippling price.

"He's still beautiful outside," said one of Ali's medical team at the time.

"But what has it done to him inside?"

The answer is chillingly apparent today as the man whose wit and repartee matched the speed of his fists is imprisoned in the mask of Parkinson's syndrome, the mind still active but the body irrevocably slowed after the impact of too many punches.

Ali's win over Foreman in Zaire, the famed 'Rumble in the Jungle', still astounds after repeat viewings.

Resisting the urgent entreaties of his corner, Ali rested on the ropes absorbing the punches of his increasingly frustrated opponent on his arms and shoulders before a sudden, savage assault floored the startled Foreman.

At 33, Ali had already passed the age when any boxer should retire.

Driven by the twin imperatives of financial demands from his expanding entourage and a healthy ego he agreed to a third fight with Frazier, the man who beat him in 1971 after Ali had lost his best years to a ban following his refusal to be drafted into the army during the Vietnam war.

Frazier, a proud and decent man who became world champion by default when Ali was forced into exile, had won the Madison Square Garden contest on merit.

Maybe something still rankled with Ali four years later when he taunted Frazier before their Manila fight by comparing him to a gorilla, a slur resented not only by his opponent but also by many of Ali's supporters.

When the pair finally stepped into the ring on October 1, 1975, the tension was palpable and the atmosphere electric in one of the last great heavyweight fights of the 20th century.

Ali dominated the early rounds before Frazier hit him with a left hook in the sixth which would have floored anybody else on the planet.

Any lingering doubts among the onlookers about Ali's caliber as a boxer were extinguished when the fastest and classiest heavyweight of any era showed he could take as well as give a punch.

Frazier dominated the middle section of the bout as the two men traded a lightning series of punches in the suffocating humidity which made even breathing an effort.

But he could not land a decisive blow and in the 12th round the incredibly resilient Ali counter-attacked, closing Frazier's left eye.

At the end of the penultimate round, Frazier's corner had seen enough.

"Joe, the fight's over, I'm stopping it," said his chief cornerman Eddie Futch.

"You're taking too much punishment and I don't want you to take any more."

Ali later paid a gracious tribute to the man who had forced him to the limit.

"Of all the men I fought in boxing, Sonny Liston was the scariest, George Foreman was the most powerful, Floyd Patterson the most skilled.

"But the roughest and toughest was Joe Frazier. He brought out the best in me and the best fight we fought was in Manila."