To describe the focus on the Melbourne Cup by the Williams family as a magnificent obsession is to merely commit a magnificent understatement.

The scion of the organisation, property developer and casino boss Lloyd Williams, has spent a lifetime in pursuit of this holy, but ultimately attainable, grail.

Fortunes have been spent in the process on horses from, firstly, New Zealand and, latterly, Europe as he chases the perfect blend of stamina, toughness and speed required to triumph in Australia's greatest race, and there's been glorious successes along the way.

If it is the pinnacle of any owner's dream to win one Melbourne Cup, then Williams could be said to be positively gluttonous.

Having whetted his appetite for Cup glory first with Just A Dash in 1981, he feasted further on What A Nuisance (1985) and Efficient (2007) before gorging on Green Moon on Tuesday, an astonishing fourth triumph in a race that most owners struggle to even have a runner in.

Once a leviathan punter, the former Xavier College boy, whose fortune has been put between $700 million and $800 million, is these days more of a recluse - rarely seen at his once familiar haunts, Flemington, Caulfield and Moonee Valley.

Like Banquo's ghost at Macbeth's feast, his physical presence might have been absent at the Cup, but his spirit and the influence of his successor, son Nick, was readily apparent as Green Moon raced to a comprehensive victory.

Once stoutly bred New Zealand stayers were Williams' Cup weapons of choice. Then he shifted his emphasis to stamina-packed European gallopers.

But Green Moon is a horse in the new Williams template - a 2000-to-2400-metre specialist bought out of a European stable, but one recalibrated for Australian racing conditions and then sent to do battle in perfect condition on the one day that matters more than all others combined to his obsessive owner.

Robert Hickmott is listed in the racebook as Green Moon's trainer, but, as Nick Williams explained, it is his father, who watched the race on television at the family's 121-hectare Macedon Lodge training complex close to Hanging Rock, who calls the shots. After 50 years in the business and having had some of the nation's top trainers looking after his gallopers, it would be hardly surprising if Williams had not picked up some of the secrets of the best along the way.

''It's his dream, he's a great strategist in everything he does. Every moment in these horses' campaigns are planned down to a tee and he is literally over the moon about it,'' Nick said. ''Anyone that ever gets into racing or bought a 1/100th share in a horse, whether it's a sprinter or a stayer, has that dream one night, that they would love their horse to run in the Melbourne Cup. We are just a bad example of that taken to extremes.''

He struggled to recall how many runners his father has had in the Cup over five decades, but stressed it's never easy to even get one to the post.