Even Steve Williams, his long-time caddy, was awed by his landmark 50th PGA Tour victory in the Buick Open at Warwick Hills in Michigan on Sunday.

"I've never seen him swing his clubs better," a revved-up Williams is reported to have told television commentators in Michigan.

And that might precisely be one of the great secrets of Tiger Woods' greatness.

He's never satisfied - as he made clear to the media on Sunday when he told them, "It's a lifelong ambition to get better."

He knows a man's swing must change as he ages and different muscles fall away or come into play.

He is further driven by a burning desire deep within, much of it instilled from an early age by his late father Earl, and enlighted by a clear awareness that the prefect swing is fleeting - in his words: "You never have it. You may borrow it occasionally for a couple of swings here and there" - he is always working and tinkering with it.

Some say too much.

Certainly there were raised eyebrows when he abandoned the early swing that had earned him three US Amateur titles and then, less than a year after he had turned professional, the 1997 Masters and three other PGA Tour titles.

Wagging fingers and a lot of 'I told you sos' replaced the raised eyebrows when the Tiger looked to have been tamed in 1978 when he could win only the Bell South Classic and blew out in all the majors.

The majors continued to elude him in 1999, but things were certainly beginning to look up again. He won nine tournaments world wide and finished in the top five in four others.

But Woods and his swing coach Butch Harmon really had their fed-faced detractors swallowing their words when he stormed into the 21st Century in 2000 by capturing a phenomenal 10 titles including the US Open, The (British) Open and the US PGA championship.

It was a stunning year and it continued on into 2001 when he won the Masters for a second time to become the first man in history ever to own all four modern majors at the same time.

The purists refused to credit him with a Grand Slam, claiming that this could only be earned by winning all four majors in the same year, so the word TigerSlam was coined.

Woods has moved on again from those heady times, which probably will never again be repeated in a new era when the golfing world has been made so aware by the long-ruling No 1 that you won't get to where he is without huge amounts of toil, sweat, and dedication, without keen analytical powers and without the strong head his Asian mother's Buddhist background has helped to give him.

Phil Mickelson, for instance, has followed Tiger's example and upped his anti, not so much when it comes to physical fitness, which is all too plain to see, but certainly in so far as the mind games go and, because of it, has rid himself of that hated tag 'the best active golfer never to have won a major' by winning three in the past couple of years.

But as I said, Woods has moved on and parted with Harmon, sadly a little acrimoniously, but he is still changing his swing on an on-going basis - and is likely to continue doing so until the day he can no longer swing a club.

In 2004 the Woods doubters came out of hiding once more, challenging the wisdom of another swing change on the grounds that his only stroke play victory came in his own silly season event, the Target World Challenge.

There was also the feeling that his marriage to his beautiful Swedish wife, Elin, would rob him of some of his intense combativeness, but again, in 2005, he hit back with a vengeance, winning both the Masters and the Open Championship and finishing 2nd at the US Open and tied 4th at the PGA.

A disastrous US Open this year where he missed his first cut in a major following the death of his father and his longest mid-season break ever once more had the doubters wondering whether they were beginning to see cracks in the granite fibre of this super being.

But back he came, this time looking unstoppable again in winning his 11th major at this year's Open Championship - and then as if to underline the fact that he was still the dominant force in the game, he went out two weeks later to capture his second Buick Open - his 50th US PGA Tour event in just his 196th start and at the tender age of 30.

Tiger Woods is not the most lovable character that has ever roamed the great golf courses of the planet Earth - not in the way that Arnold Palmer or Seve Ballesteros were at their peaks.

He is so focused so often that too often he is seen as intense and unsmiling and - he can hardly be called a sparkling humorist.

But that he has charisma and a huge following is certainly not in doubt. Nike and his other sponsors would not be paying him some $87m and making him the richest sportsman in the world if he didn't have it

What then makes him the icon that he is.

Is it respect for a passionate man who clearly loves his family and his life, loves (and respects) the game he plays, and, of course, loves to win as much as his galleries love winners.

Is it sheer class and an amazing game that have produced some of the most memorable shots of his generation.

Or is it his ability to keep learning, keep practicing - and keep coming up with the goods.

I would have to say it's all of these things, tied together by a seed sewn by his father a long time ago that has flowered an enormous drive to be the best in the world.

How long will it last?

Long enough to beat Jack Nicklaus' record of 18 majors won? Or to surpass Sam Snead's 82 Tour victories?

Tiger is humble on those two.

"It's going to take a lifetime, a career basically, to get to that point," he told the media in Michigan on Sunday.

His triumphs will probably become fewer in his latter years, but at 30 he is in his prime and already ahead of the record setters, so don't be surprised if he does it sooner than later - and that before he is finished, he has become the greatest golfer that ever lived