Irish raider State Of Rest edged out Anamoe to be first across the line after a stirring duel in the Moonee Valley straight.

But Anamoe's jockey Craig Williams claimed there was interference over the final stages and that had cost the three-year-old certain victory in a brilliant weight-for-age contest.

The winning margin in favour of State Of Rest was a long head.

Williams fired in a protest with the hearing lasting more than 30 minutes before stewards dismissed his objection.

"The longer (the protest) went on the more anxious I was getting," winning jockey John Allen said.

In a race that changed complexion on the home turn, State Of Rest charged to the lead only for Anamoe to trail through underneath.

State Of Rest shifted his ground toward the rail and hampered Anamoe but stewards found the interference was not enough to change the result.

The victory continued young Irish trainer's Joseph O'Brien's love affair with Australian racing.

He joins his father Aidan O'Brien as a Cox Plate-winning trainer while the 29-year-old has also led in two Melbourne Cup winners.

Verry Elleegant took the minor placing in a race robbed of a major drawcard when early favourite Zaaki was scratched because of an elevated temperature.

Allen produced one of the great Cox Plate rides and it didn't deserve to be denied with an overturned result.

Once a struggling jockey in Ireland, Allen has found his niche in Australian racing and he delivered with a daring piece of horsemanship to secure his place in the Cox Plate history books.

Allen navigated an inside path and when a run appeared, State Of Rest responded to hit the front.

But Williams and Anamoe were hot on his tail and they settled down for one of the more memorable Cox Plate finishes that came with an obvious twist.

"When the gap appeared I had to ask him to improve quickly before it closed and we might have got there a little too soon, but to his credit when (Anamoe) got to me, he really fought.

"It was a ding-dong battle and luckily we got our head down on the line."

Head Of State started at $7.50 as Anamoe shared favouritism with Verry Elleegant at $3.60.

Verry Elleegant also loomed large in the straight before finishing a length behind State Of Rest.

"I thought I was the winner down the side but to the first two's credit they gave a kick and it was a margin that I couldn't pull back," jockey Damian Lane said.

Long-time favourite Zaaki was withdrawn on race morning.

"These things happen and it's just unfortunate timing," trainer Annabel Neasham said.

Zaaki's stablemate Mo'unga was one of the best-backed runners at $5.50 before finishing fourth.

Australian Associated Press