The race that has everything has gone to a horse which had nothing.

Shamus Award, a colt whose place until Saturday had been on racing's lowest rung, won arguably Australia's greatest race, the $3 million Cox Plate.

It doing so, he defied the country's best horses and some of the world's most powerful racing stables.

And he did it in the hands of teenage apprentice Chad Schofield, who was suspended the night before the race and outrode some of the biggest names in the game.

Until last Tuesday, none but Shamus Award's trainer Danny O'Brien and his owners had any notion their colt would even be in the race - and in the opinion of many, he shouldn't have been.

Shamus Award had never won a race before Saturday.

In nine starts he'd been placed seven times and was the first maiden in 20 years to even be accepted into what is generally regarded as an elite field.

But O'Brien watched as the number of likely acceptors dwindled on Tuesday morning and took a punt by paying up.

"The worst that could happen was they'd kick me out," O'Brien said.

The Moonee Valley Racing Club committee voted to give Shamus Award half a chance, making him the first emergency.

Then came the scratching a couple of hours later of the nominal favourite Atlantic Jewel, and Shamus Award was in the 14-horse field that is meant to represent the cream of Australian thoroughbreds.

While Shamus Award went into the Cox Plate without a win, he'd won $260,000 and wasn't the average maiden.

"He's been a high-class colt ... he was a maiden going into today because a few things hadn't gone his way in the Guineas," O'Brien said.

"We certainly went in knowing he was in great order.

"He'd had the perfect preparation to go the 2000 metres. He had 49-1/2 (kg) on his back, and once he drew well we were always going to be aggressive.

"And Chad gave him a peach of a ride."

It was a messy race in which the favourite It's A Dundeel couldn't get closer than three-wide throughout and one-time Melbourne Cup favourite Puissance De Lune floundered.

However, Shamus Award rolled along in front with Schofield gradually slipping him rein from the 1000m.

"He travelled beautifully, really sweetly," Schofield said.

"Fiorente was outside him and we beat him off before the turn. At the 200 I thought I had it won."

But on the line he thought he'd lost it as Happy Trails, a horse with a story to rival the winner's, lunged at him.

Shamus Award ($21) hung on to score by a half head from Happy Trails ($12), whose trainer Paul Beshara was disqualified a week ago for treating the horse on a day last month on which he was due to race.

Fiorente ($8) ran a typically brave race to finish third, a long neck further back with the favourite It's A Dundeel eighth.

Shamus Award, which increased its racetrack earnings by almost 800 per cent with a winner's cheque of $1.8 million, will now rest until the autumn.

And he'll return with his name on the most coveted honour roll in Australian racing, to be forever known as the first maiden to win the Cox Plate.