It was his longest bout, and one that ultimately he could not win.

But Muhammad Ali’s long struggle with Parkinson’s, to which he succumbed on Friday night, only served to increase the worldwide admiration he had gained before the disease robbed him of his powers.

Ali would come to call it his "trial”, a challenge to endure and overcome.

When the superstar began displaying the symptoms of the disease- such as slurred speech and slow body movement – during the late 1970s, it prompted wild speculation among a public not yet familiar with the reality of Parkinson’s.

This included the suggestion that Ali was battling deep-seated psychological problems or suffering the results of substance abuse.

Indeed his condition was not properly diagnosed as Parkinson’s until 1984, three years after he retired from the boxing ring.

It is now generally accepted that the disease – which attacks the nervous system and affects one in 500 people - was the result of Ali taking too many blows to the head, particularly in the final years of his career.

Following his four year ban from the sport for refusing to fight in Vietnam, Ali returned to the ring in 1970, having lost some of the speed and lightning reactions that had made him unbeatable during the sixties.

In a dramatic change of tactics he adopted what he called the ‘rope a dope’ technique against George Foreman, in October 1974, and Joe Frazier the following year, in which he absorbed his opponents’ blows until the other fighter was too tired to respond to Ali’s counter-attack.

What followed only aggravated the neurological damage Ali had begun to suffer as a result of these brutal encounters.

In 1978, his speech already beginning to slur, Ali lost the heavyweight title to Leon Spinks, before regaining the championship from him seven months later - the first time anyone had won it on three separate occasions.

Two years later, at the age of 38, tempted back into the ring by money and his love of the crowd, he suffered a terrible beating at the hands of Larry Holmes, his former sparring partner. In 1981 he took another pummelling, losing on points to Trevor Berbick before finally retiring for good.

By now Ali’s physical deterioration was obvious. He suffered from permanent fatigue, his mouth drooled saliva and he developed a tremor in his hand.

During a 1991 US television interview with Bryant Gumbel, his speech heavily slurred, Ali appeared to refer to his condition as a "trial” from God and spoke of preparing for death.

He said he thought about it during each of his five daily prayers, but he did not give the impression it prayed on his mind. If anything he seemed at peace with the idea.

"I might die tomorrow, I might die next week. I don’t know when I’ll die,” he said.

Ali admitted to Gumbel that the effects of Parkinson’s had made him fearful of appearing and speaking in public.

But he added that it was something he had to strive to overcome: "I realise my pride would make me say no, but it scares me to think I’m too proud to come on this show because of my condition.”

In 1996, Ali faced down those fears on one of the biggest stages of all, when he stepped out of the shadows to light the Olympic flame at the Atlanta Games.

The debilitating effect of Parkinson’s was now evident to everyone watching the opening ceremony. His arms shook violently, as did his upper body, moving many in the arena to tears as he struggled to overcome the physical effects of his condition to hold the torch aloft, before reaching down and lighting the cauldron.

Janet Evans, the American swimmer who handed him the torch, said: "It was all about courage. It was written all around his body that he was not going to let [it] do him in. He was still the greatest.”

Ali’s subsequent public appearances became ever more poignant, as Parkinson’s continue to ravage his mind and body.

In October last year Ali, a shadow of his former self, appeared at a Sports Illustrated tribute to him at the Muhammad Ali Centre, in his hometown of Louisville, Kentucky. His last public appearance came in April, when - hunched over and wearing sunglasses - he attended the annual Celebrity Fight Night dinner in Phoenix, which raises funds for treatment of Parkinson's.

It was a tragic end to what had been a majestic life, but Ali appeared to acknowledge it would in part be one of his own making.

In 1975, speaking about those punishing fights with Foreman and Frazier, he said: "I once read something that said – ‘He who is not courageous enough to take risks will accomplish nothing in life.’ Well, boxing is a risk and life is a gamble, and I got to take both."

Agencies