Marmelo ably justified 11-8 favouritism to win the Listed Sky Bet Grand Cup at York.
The Group Two-winning five-year-old was a pleasing runner-up on his comeback in May and made no mistake in a course-record time over a mile and three-quarters.
Frankie Dettori was keen to seize the initiative aboard Weekender, who was still in front two furlongs from home.
John Gosden’s inmate was outflanked by Marmelo and Duretto once push came to shove, but he fought back creditably to finish second.
Marmelo was nonetheless on top at the line and was good value for his neck triumph under Ryan Moore.
Duretto finished third, another three-quarters of a length away.
Moore said: “He’s a big boy and it was probably quick enough for him.
“He travelled very smoothly. He’s a very likeable horse.”
Morrison said: “He’s won despite the ground, I think. He’d prefer more cut but that’s two course records he’s got now – he’s also got one at Chantilly.
“As he proved in Australia, he’s not a slow horse. A mile and a half is within his compass.”
“My head lad Tom Pirie has done a fantastic job with him. He rides him every day and never left his side for two months is Australia.
“We’ll go back to France next for the race he won last year (Prix Kergorlay) and then go back to Australia – he is part-owned by Australians.
“I think he’s still improving. A sound horse should keep on improving until they are six.
“There are just more races that suit him in France and he qualifies for the premiums, hence why he’s there more than here.”
Moore was suspended two days for using his whip “without giving the colt time to respond” in the final half a furlong.