Defeated only once in nine previous career starts, Palace Pier was favourite to make it four from four for the season under Frankie Dettori, having missed last month's Sussex Stakes at Goodwood following unsatisfactory blood test results.
Always travelling strongly, John and Thady Gosden's stable star moved smoothly into contention on the outside of the field, with Jim Bolger's 2000 Guineas and St James's Palace Stakes hero Poetic Flare delivering his challenge close to the stands' rail.
In receipt of 6lb from his older rival, Sussex Stakes runner-up Poetic Flare did his best to claw back Palace Pier inside the last half-furlong, but Dettori's mount was always doing enough to hold him at bay.
The Aidan O'Brien-trained Order Of Australia finished third to make it a clean sweep for the visiting party.
Gosden said: "I lost a lot of time with him. He had a blood disorder which prevented him from running in the Sussex Stakes. To be perfectly frank, he came here with here with the minimum amount of work.
"Frankie said that his class made the difference. He was blowing a lot afterwards.
"However, if you bypass the Prix Jacques Le Marois, you've missed the race of the year. Of course, coming back here was the long-term aim. All things being equal, I ran a horse that was 80 per cent fit.
"He had the class and the jockey too. You could see that he was starting to tire towards the end, due to the fact that he had been held up in his work because of his illness.
"It was a super edition of the race and the second is an iron horse.
"I would have liked to have had him 100 per cent as last year. However, he ran a blinder and his trademark acceleration came to the fore."