Gold Trip, ridden by Mark Zahra, won the Melbourne Cup at Flemington Racecourse on Tuesday, thundering home in the final straight to win Australia's "race that stops the nation" by a length and a half from Emissary.

The six-year-old stallion trained by Ciaron Maher and David Eustace, rated an 18/1 chance by bookmakers, charged in front at the 300m mark to win a thrilling sprint to the final post in the gruelling two-mile handicap.

High Emocean, also trained by Maher and Eustace, placed third on a rain-softened track.

"I feel like crying. It’s unbelievable. What a day," said winning jockey Mark Zahra.

"He’s a horse that when you go, you don’t give him a chance to think about it. I was hoping no one would come near me. It’s just elation when I crossed the line."

The field of 24 was reduced to 22 after Point Nepean was scratched on Monday and Lunar Flare failed a veterinarian inspection on the morning of the race.

The Cup ran after police were called to investigate alleged vandalism at Flemington in the early hours of Tuesday morning, with video on social media showing a hand-held hose discharging an oily, black substance onto the track.

The Nine Network said an unnamed person contacted the broadcaster and claimed responsibility for pouring the sludge as a "problem gambler" making a protest against the Victorian Racing Club.

The Victorian Racing Club runs the Melbourne Cup and other race meetings at Flemington. (Reuters)