Why Muhammad Ali was such an inspiration to millions across the world

At the height of his career he probably was.

The boy from Louisville, Kentucky, baptised Cassius Clay, soared to world fame not only as a boxer but as a unique personality.

His emergence as a totally dominant world heavyweight champion was the greatest thing that ever happened to boxing, and when he retired he left a void in the sport almost impossible to fill.

But the fact that he stayed too long, had too many fights, and ended up with brain damage, did boxing harm.

"If it could happen to Muhammad Ali, the man who was in a class of his own, it could happen to anyone," the critics claimed.

When he set out on his professional career after winning an Olympic gold medal in Rome in 1960, Cassius Clay was the man least likely to come to harm in his new rugged environment.

But by the time he retired in 1981 after being outpointed by a moderate, light-punching Canadian, he had been in 61 fights, many at the highest level, and countless hours of training. The accumulation of wear and tear was too great even for this remarkable man.

The tragedy of his life was that he felt the need to go on for as long as he did. But money had a habit of slipping through his fingers, and alimony and maintenance cost him a fortune.

There was also the need to express himself, and he did it better in the boxing ring than anywhere else. So, at an age when he should have been thinking of putting his feet up, he was defending his world heavyweight title against all comers. They were not necessarily difficult fights, but they all took something out of that marvellous frame.

Then came the final mistake. After giving up the championship in 1979 he typically felt the need to come back a year later and fight Larry Holmes.

Ali was then 38. He had weight trouble, training was more arduous, and Holmes stopped him for the only time in his life. Even then he had one more fight. He took on the Canadian, Trevor Berbick, and suffered a second successive defeat for the first time in his life. Then he retired for the last time - several years too late. From then on, his health became a constant worry to those closest to him.

Ali won 56 of his 61 contests. The others to beat him were Ken Norton, who also broke his jaw in the second round of a 12 rounds fight, Joe Frazier and Leon Spinks.

Frazier was the prime enemy. He and Ali met three times and they developed a huge respect for each other. But when they fought, if it had to be to the death, then so be it.

Their first fight was in 1971. Frazier was champion, as a result of Ali's three-year exile from the sport because of his refusal to be drafted for service in the US Army, and he beat Ali on points.

He also knocked him down with a left hook near the end of the 15 rounds, which raised the thought that Ali might be fallible after all. Britain's Henry Cooper had raised the same thought with the same left hook in London eight years earlier.

In 1974, while George Foreman held the title, Ali gained his revenge over Frazier on points over 12 rounds, and 18 months later he won the decider, stopping Frazier in 14 rounds in the "Thriller in Manila".

In between times, Ali had taken Foreman out in eight rounds to regain the title, and it was the three Frazier fights, added to the Foreman experience, all in the space of three years, that probably sowed the seeds of Ali's physical trouble.

For both Frazier and Foreman were fearsome punchers and Ali had a perverted pride that seemed to make it necessary to put his chin to the test. Both men were given free shots at the target as Ali set out to prove himself the strongest man in town.

Ali was good to his fellow professionals. From the day he beat Sonny Liston in 1964 to open his championship account, he regarded the title as an object with which to make money, for others as well as himself.

After the ritual return with Liston had taken place - it lasted less than a round - the world heavyweight championship was there for anyone to win if he was good enough.

There were some highly improbable challengers but any heavyweight with reasonable pretensions was given his chance. Ali defended in London twice in 1966, allowing Henry Cooper and Brian London nine rounds between them.

By March 1967, when he defied the draft board and the US government on the Vietnam issue, he had been in 10 world title fights. He had also changed his name from Clay to Ali and was heavily involved in the Black Muslim movement - and his popularity among his fellow Americans had dropped sharply.

But there was no turning back, for Ali was always his own man. Born in the south, he knew a few things about racial prejudice in the United States and was in the forefront of the fight for equal rights.

His most dramatic gesture however was performed for his own satisfaction and not for publicity. Just before his first professional fight, the young Cassius Clay threw his Olympic gold medal, from which he had been inseparable, into the Ohio river.

He had won it for Louisville and America, he said afterwards, but his town and his country still made him buy hamburgers in a segregated restaurant.

When he preached a sermon in an apostolic church in 1983, his text was: "Why are all the angels white? Why ain't there no black angels?"

The 1967 episode spoiled his popularity, but did not detract from the attractiveness of a man who was not only an exceptional heavyweight champion but a wit, a personality, and a refined clown.

Ali's self-advertisement sometimes reached ridiculous proportions. As a braggart he had no equal, but the humour in it was never hard to find.

He also had great talent as a debater as one British television interviewer, who started with every advantage, found to his cost. Ali loomed over us, larger than life, for so long that he seemed to be immortal.

In later years, he made goodwill missions to Afghanistan and North Korea; delivered much needed medical supplies to an embargoed Cuba, travelled to Iraq and secured the release of 15 US hostages during the first Gulf War; and journeyed to South Africa to meet Nelson Mandela upon his release from prison.

He was instrumental in providing more than 232 million meals to the world's hungry. Travelling across continents, he hand-delivered food and medical supplies to children in Ivory Coast, Indonesia, Mexico, and Morocco among other countries.

He also helped charities at home, visiting countless soup kitchens and hospitals, and helped such organisations as the Make-A-Wish-Foundation and the Special Olympics. At the State Capitol in Michigan, he advocated new laws for protecting children.

Every year he took part in "Fight Night", which generates funds for the Muhammad Ali Parkinson Research Centre at Barrow Neurological Institute in Phoenix, Arizona.

Once dubbed "Mr International Friendship", by President Jimmy Carter, Ali received many awards for his humanitarian efforts.

These included a UN Messenger of Peace in 1998-2008, for his work with developing nations, the Presidential Medal of Freedom in 2005, the USA's highest civil award, Amnesty International's Lifetime Achievement Award, and Germany's 2005 Otto Hahn Peace Medal, for his involvement in the US civil rights movement and the UN.

He was also recognised many times for his contributions to sport. His honours included Sports Illustrated's "Sportsman of the Century", BBC's "Sports Personality of the Century" and GQ magazine's "Athlete of the Century" .

At the Atlanta Olympics in 1996 he received a gold medal to replace the one he threw away in 1960.

Ali appeared in several motion pictures, including the big-screen adaptation of his first autobiography, The Greatest, playing himself.

His life was the subject of numerous films, including the Academy Award-winning documentary When We Were Kings and Michael Mann's biopic, Ali, starring Will Smith.

It was a measure of the hold he had on the boxing business that, when he finally left it and Larry Holmes took over as the big man and ran up an even more impressive record, the public were inclined to ask "Who is Larry Holmes?"