Godolphin has come out on top in a clash between two of racing's superpowers, with Hartnell a dominant winner over Japan's To The World in the BMW at Rosehill.
Punters saw Saturday's race as a battle between $2.60 favourite To The World and former English horse Hartnell ($3.10), which caused a pre-race scare when he got his front legs over the barrier.
After the vet gave the OK, James McDonald jumped back aboard for one of his most important wins since joining Sheikh Mohammed's team.
Hartnell and To The World settled midfield with outsider Fast Dragon setting a strong tempo at the front.
To The World lost some ground when Opinion put in a couple of short strides before the turn and was eased out of the race, but Hartnell was the strongest stayer at the end of the 2400 metres.
He had 1-1/4 lengths to spare over his rival, with Beaten Up ($101) another half neck third.
"Looking at the race it looked as if we had two very special horses here today and it was an exciting race," Hartnell's trainer John O'Shea said.
"I was a bit worried when he played up before the race and relieved when they let him start.
"It was evident that we might have had the Japanese horse's measure, so that was very exciting.
"Hartnell is a lovely horse and he's beaten a world-class horse here."
Hartnell will head to the Sydney Cup (3200m) while To The World is bound for the Queen Elizabeth Stakes.
To The World's jockey Nick Hall said he lost about a length in the incident with Opinion.
"The winner outstayed us," Hall said.
"He was a bit weary at the end. I tried to come around horses but when Opinion broke down he lost a length."
Fortunately, Opinion didn't break down, but was pulled out of the race by Tye Angland, who thought something was wrong.
"His action changed completely," Angland said.
"There is a bit of blood in his mouth, so he must have bitten his tongue.
"But I retired him because he didn't feel 100 per cent."
Opinion's Chris Waller-trained stablemates Beaten Up and fourth-placed Who Shot Thebarman both pleased their connections.
"We are undecided where Beaten Up goes next, but Who Shot Thebarman put in a great trial for the Sydney Cup," Waller said.
Who Shot Thebarman finished third in the Melbourne Cup won by Protectionist, which put in his best run this campaign when he charged home for fifth with last year's winner Silent Achiever sixth.
O'Shea said he would discuss the next move for Hartnell with the Godolphin team.
"We've got him in the Sydney Cup with 52 kilograms and we've got Contributer in the Queen Elizabeth Stakes, so we will have a think about it," he said.