Ali the icon still resonates at 70
It is now more than 30 years since Muhammad Ali retired from boxing. For much of that time he has been battling Parkinson's disease, his public appearances becoming rarer and rarer as his physical condition has worsened.
But for those who question whether he still resonates with the sport, I would suggest a trip to the Lynn boxing club in Peckham, south London.
I spent a couple of hours there on Monday evening, filming a special report on his 70th birthday for BBC News. Despite the freezing weather, around 20 boys, and young men and women had turned out to train and spar.
When I spoke to some of them I was amazed to find that even boys as young as 11 had watched most of Ali's classic fights and studied his technique and style intently.
As we played them replays of his fights on the wall of their gym, one or two mimicked his moves, trying to absorb a bit of the magic they were seeing.
Ali, of course, will always hold a special place in British affections.
As ITV's excellent documentary 'When Ali came to Britain' pointed out, initial hostility at his brash trash talking quickly gave way to warmth as his charisma won over the public.
His frequent visits and TV interviews here cemented his status and, although he often faced tough questioning on his divisive religious and racial views, he relished the greater freedom he seemed to enjoy in Britain.
Decades on, his power as a sporting icon grows ever greater. He remains the most recognisable figure in sport, regularly topping sporting celebrity polls around the world.
His ability to generate cash also remains huge.
He earned $55m (£35.75m) in 2006 and although that was a high point, he still generates between $3m and $4m a year for CKX, an entertainment-business based in New York which owns 80% of his image rights. (Just for the record, CKX also own the lion's share of the image rights to Elvis - not a bad American double act.)
I never saw Ali fight in the flesh. Like those youngsters at the Lynn club, I have to rely on replays to experience those amazing nights in Zaire or Manilla, moments when the world seemed to stop for heavyweight boxing.
But you didn't have to see him fight in person to understand his significance - both as a fighter and as a man of history, someone who shaped rather than just reflected events. Who else in sport can compare?
Tiger Woods perhaps matches his sporting achievements and as a black man in a predominantly white sport potentially carries similar cultural resonance.
But while we now know a bit too much about his private life, who can say they know anything of Tiger's beliefs? He is a sporting giant for the corporate age and honesty tends to be bad for business.
Watching one or two of Ali's interviews with Sir Michael Parkinson again, I am amazed at the level of scrutiny he was subjected to.
It's impossible to imagine any sportsman or woman now holding such controversial views on race, religion or, of course, his rivals - let alone being prepared to be questioned on such subjects.
We live in a more deferential age and sport is much the poorer for it.
On Saturday night in his home town of Louisville, Kentucky, a few hundred carefully selected guests gathered at the Muhammad Ali Centre to celebrate Ali's 70th birthday.
It was supposed to be a behind-closed-doors, private event. But Ali the showman couldn't resist.
As the crowd sang happy birthday to him, Ali stood on a balcony above them and raised a hand. It was a small gesture but it was acknowledgment of the enormous regard in which he is still held.
Afterwards one of Ali's daughters told reporters he was now entering the most dangerous phase of Parkinson's when he is most susceptible.
But Ali has spent his life defying doubters and confounding expectations. Who would dare write him off just yet?
David Bond's report on Ali will be broadcast on BBC News at 1800 and 2200 GMT on Tuesday, 17 January.