He will be 70 tomorrow yet even though the dancing years have ebbed away and the famous shuffle is no longer a dazzling quickstep but a distressingly slow wobble, he remains the most recognisable human being on earth, and among the best-loved

There has only ever really been one Lord of the Rings. "Parachute me into High Street, China," he once said at his zenith, "and every kid would know who I am."

I was fortunate enough to travel the world with the phenomenon who so ennobled his art that his act as the undisputed heavyweight champion has proved impossible to follow.

Sport's biggest irony is that the greatest orator it has known is now reduced to a mumble, the face that launched a thousand quips partially paralysed, like much of his body, through Parkinson's Syndrome, the nerve-numbing condition from which his housepainter father died, but in Ali's case surely was acerbated by having ten fights too many.

His becoming a septuagenarian will be marked by a birthday bash in his hometown Louisville at the downtown cultural centre and museum that bears his name, a name emblazoned on a boulevard, buildings and street signs. Another tribute is planned for Las Vegas, the scene of so many of his triumphs, and sadly of his eventual demise.

In 50 years of covering international sport there have been moments when I have been tempted to shed a tear; but only once have I ever done so.

That was on the night of October 2, 1980, in the car park of Caesars Palace where an 18,000 crowd had assembled what was to prove Ali's penultimate fight.

It was the night an icon disintegrated before our eyes as Ali, a 38-year-old robotic shell of the  sublime athlete of his heyday, suffered a savage beating that even his opponent, Larry Holmes (pictured left), was reluctant to administer, repeatedly beckoning to a dispassionate referee end his erstwhile idol's agonising humiliation..

At ringside even the media were pleading "stop it, stop it" amid counter cries from some in the Ali entourage fearful of losing their meal ticket.

It was Ali's career-long cornerman Angelo Dundee who finally defied them. "I am the chief second and I stop the fight," he yelled to the referee, a dull-eyed Ali slumped on his stool at the end of the tenth round. It was too late to save Ali's career, but it probably saved his life.

Ali had reigned in an age when boxing crowns were not tawdry bits of bling. He turned it into an art form, making a ballet out of brutality.

Being a sportswriter around him was bliss. We were never short of a storyline.  Once, back in the 70's, on arriving to interview him in Dublin, we discovered that Ali was flu-stricken and being attended by a doctor in his hotel bedroom.  We explained to Dundee that all we wanted was to talk to Ali for ten minutes.  "No chance," came the reply.  "He never talks to anyone for less than an hour."  He phoned Ali's room and winked. "Hey guys, the champ says go on up."  We emerged two hours later, notebooks overflowing.

Not that Ali was a saint. He was a serial womaniser and had a darker side which surfaced after he became champion and a member of Malcolm X's Black Muslim movement. Perhaps understandable considering the past injustices to his race by white America. Previously barred from a local fast food restaurant because of his colour, when he returned from Rome after winning the Olympic light-heavyweight title in 1960.he placed his gold medal on the counter, and ordered a hamburger. "We still don't serve niggers," he was told. "That's ok," the then Cassius Clay is said to have cheekily replied. "I don't eat 'em!"

It was as a brash 18-year-old Cassius Marcellus Clay, that he had defeated defeating Polish opponent Zbigniew Pietryskowsky in the Olympic final, showing early signs of the uniquely flamboyant, fast-fisted style that was to become his hallmark.

He was so proud of his gold medal that he didn't take it off for two days. Born on January, 17, 1942, the younger of two brothers (Rudolph Valentino Clay was later to box as Rahman Ali) he was named after the 19th century slave abolitionist and politician, and brought up a Baptist. As a 12-year-old Clay had taken up boxing on the advice of a white Louisville police officer, Joe Martin, after saying he wanted to "whup" the thief who had stolen his bicycle. He went on to win two National Golden Gloves titles recording 100 wins and five losses. In an early biography he claimed he threw his Olympic medal into the Ohio River in disgust after being refused service at a 'whites-only' restaurant. He later admitted he actually lost it and was given a replacement during the 1996 Atlanta Olympics when his shaking hand lit the flame in one of the most moving moments in the history of the Games.

One of Ali's nine children, Hana tells a story which probably sums up what the world felt about her father. She recalled how, soon after he became ill, she met him for a pizza dinner near her home in Los Angeles. Afterwards they walked out into the balmy California evening, a tramp approached. "He smelled quite badly and was in a terrible, filthy state. I reached into my purse to give him some money but the vagrant shook his head and said: 'No. I just want to hug your dad.'

"Before I knew it Dad had his arms around this man and was hugging him in the middle of the street. Both of them were crying. Then dad took him inside the restaurant, ordered him a meal, and sat with him."

Primary school teacher Hana and her sister Laila, who became a professional boxer much to her father's chagrin, were born during Ali's third marriage to model Veronica Porsche. He had four other children, including identical twins, with second wife Belinda and two others were born out of wedlock to two different women.

Ali always was a ladies' man and it was the ladies in his life, those who were his family, who nurtured and cared for him. "It was difficult for him to be a normal father because we had to share him with the world but when I see how other celebrities mess up their lives I realise he did a great job," said Hana

Philanderer he may have been in his boxing years – Dundee once caught him doing some horizontal jogging with a female journalist after a title fight weigh-in - but in retirement it was the love of one good woman that helped keep him alive. His fourth wife, Lonnie, had devoted her life to nursing him since they were married in 1986. Ali called her "The Boss".  She accompanied him everywhere, controlling his life and the purse strings. Although much of the fortune he had earned in his fighting years had dwindled, he was still able to live in comfortably as The People's Champion, earning considerable sums from personal appearances that enabled him to afford the much needed medical care. Unlike some of his predecessors he was never destined to end up destitute. But money was not the most compelling reason that kept him in the spotlight. "The trouble with Ali is that he doesn't know how to die," Joe Frazier once remarked.

"He simply couldn't bear to fade away or be forgotten.  Being who he is, is his lifeblood," Lonnie said. She is witty, smart and gracious, a business graduate of Vanderbilt University who started cooking for him when he was getting sick.

A tall, striking woman, she grew up as Yolanda Williams and has known Ali since she was a five-year-old living opposite his family home in Louisville. She remembers him as Cassius Clay, coming home from training camp: "He just wanted to be with the kids from the neighbourhood. He had this great big bus, and he'd take us all over Louisville. He'd shout, 'Who's the Greatest?' We'd all answer, 'You are!' "

Lonnie reckons that by the time she was 14 she was in love with him. "It wasn't just a schoolgirl crush. I knew in my heart I was supposed to be with him."

Three marriages, and three horrendously expensive divorce settlements, later, they met up again in very different circumstances. He had been through a savage beating in his penultimate fight, against Larry Holmes in 1980. "I met him one day for lunch in Louisville and he stumbled getting out of the hotel lift. Something was obviously wrong. Then a friend told me he was sick and needed someone to take care of him, or he might die."

So Lonnie, who had just graduated, gave up her job with Kraft Foods and flew to Los Angeles, where he then lived. "He needed someone to be by his side and I was proud to be that someone." He was diagnosed with Parkinson's in 1985 and they were married a year later.

He and their adopted son, Assam, lived in a farmhouse near Michigan, which used to be one of Al Capone's hideouts, where with her guiding hand on his arm, he did what he always did best, and be himself, the People's Champion. "There was a quality about Muhammad that makes you want to give him all the love in the world," she said. "He is a warrior. He has always needed something to battle over."

But there is no longer a trace of malice in him. Throughout his illness he's never had an ounce of self-pity, as generous with his time as with his money. "Whenever you see him, you just want to hug him," says daughter Hana.

I know what she means. I shared a hug with Ali not so long ago, and was again close to tears when he placed a trembling hand on my shoulder and leaned down to whisper. "It ain't the same any more, is it?"

"No champ," I replied, "It ain't."

Ali hasn't floated like a butterfly or stung like a bee for over 30 years but he is still in there fighting, perversely outliving the majority of his 49 opponents, among them Sonny Liston, Joe Frazier and Henry Cooper, whose left hook back in 1963 came within a split second, or a split glove, of changing the course of boxing history.

Perhaps the most pertinent birthday tribute comes from Dundee, himself now 90. "Muhammad was great outside the ring, he was great inside it.  Right now there is nobody out there to turn people on like he did.  It is unfair to try and compare anybody with him 'cos he's a once in a lifetime guy. There'll never be another Muhammad Ali."

When Ali Came to Britain, a documentary celebrating his 70th birthday will be shown on ITV1 at 10.35pm tonight and Ali: Still  The Greatest will be screened on ITV4 at 9pm Tuesday-Friday this week.