It began with a French horse who started life running with greyhounds in a paddock in Germany, a trainer who had never heard of Flemington and an owner who didn't know where to find Australia on a map.

The same horse is now a Melbourne Cup legend and an Australian racing hero - and by Tuesday night he could be one of the racing world's greatest moneymakers.

Dunaden will go to the start of Tuesday's Melbourne Cup as arguably the race's best winner in 50 years and as one of the most unlikely rags-to-riches stories in its history.

When he took out last year's Cup, Dunaden was the property of an Arab sheikh, a member of a team of elite racehorses prepared by one of France's finest young trainers and the winner of more than $6.5 million.

He'd got to that point after 24 starts, after being bought for 1500 euros as a weanling, after being left unraced with the greyhounds, after beginning his racing career as an unwanted two-year-old in a selling race at Strasbourg and after passing through the stables of five different trainers.

Dunaden's trainer in his first campaign was Doris-Ursula Smith a small trainer in the border region of France and Germany who, at the horse's sixth start, coaxed a win from him in another Strasbourg seller.

Soon after, his new owners transferred Dunaden to French trainer Yannick Fouin who won a single race with him before he was moved on again to Alban de Mieulle.

De Mieulle trained for the father of Dunaden's current owner Sheikh Fahad al Thani and had bought the horse out of yet another seller with a view to him being a lead horse for the senior sheikh's Arabians.

Sheikh Fahad heard of this lead horse and negotiated secretly to buy him from his father.

"I couldn't let my father know I was buying his lead horse, so I had to keep my name out of it," Sheikh Fahad said.

By now Dunaden was in the Chantilly stable of Richard Gibson and Sheikh Fahad inspected him after the horse had run a slashing race first up for his new trainer at Longchamp on Arc de Triomphe day in October 2010.

"He was fat, you could see he wasn't fit," he said.

"But he had come from last in a field of 20 and he ran better sectionals than the Arc winner.

"We saw a lot of potential."

Dunaden duly won his next two starts and was placed in two more for Gibson then won his next two and was placed in two more.

But still with little hint of what was to come.

With Gibson's move to Hong Kong early in 2011, Dunaden went to his current trainer Mikel Delzangles who began his glorious association with the horse by winning the Group Three Prix de Barbeville at Longchamp, a race in which those behind him included Americain and Brigantin who are also in Melbourne for the Cup.

In that same initial campaign for Delzangles, Dunaden claimed the Geelong Cup, the Melbourne Cup and the Hong Kong Vase. This year he has added the Caulfield Cup.

When Dunaden attempts to win his second Melbourne Cup on Tuesday he will be having his 12th run for Delzangles, 41, who has won five times with him, the victories including three of the richest races in the world.

"It is an amazing story for the horse and for me," Delzangles said in Melbourne this week.

"When I started training I didn't think it is possible to take a horse from France to Australia and win a race.

"Now he has done it twice. But he is a special horse, very special."

Delzangles has made two trips from Paris to Melbourne to see Dunaden who arrived three weeks ago, staying little more than one day each time.

After the latest journey he flew on to Los Angeles where he had two runners at the Breeders' Cup meeting where Flotilla won the Juvenile Fillies Turf.

By the time he returns for the Cup he will have logged around 50,000km.

"I wanted to be sure Dunaden was well, and I'm very happy with him," he said.

"He couldn't be better."

He may need to be, however.

As well as his old foes Americain and Brigantin, Dunaden is up against the biggest team of international runners ever to invade Melbourne.

Among them is the horse he beat by a few millimetres last year, Red Cadeaux, and the highly-rated English runner Mount Athos and Galileo's Choice from Ireland.

Along with an extra 4.5kg on his back, they all make a second Cup more difficult.

"Having been here last year, we know a little more," Delzangles said.

"We know the track, the routine, and many little details which make things easier.

"I think he is better than last year, definitely. But he has to be 4-1/2 kilos better. It is difficult, but you know him, he is always fighting, always trying for the victory."

On Tuesday he will need to fight harder than ever.

And if his best is good enough he will leave Melbourne as the winner of more than $10 million, 90 per cent of which will have been collected in just four Australian races.