The New Zealand bred stallion justified his 10/11 starting price by leading home Carlton House - owned by The Queen - by two and a half lengths with the strong-finishing Farhh third.
So You Think, trained by Aiden O'Brien and ridden by his son Joseph, avenged a shock defeat in the same race last year.
O'Brien snr said: "We expected a big run today, we felt like we had him in a place that he was never in before with us, which is incredible.
"I think we've had him a year and a half and it's taken me that long to learn how to train him.
"We went back and listened to what everybody was saying about him, listened to what Bart (Cummings, former trainer) was saying and telling us what to do and what not to do. We listened at the end.
"We felt he was in a place today he's never been in before."
The jockey said: "My horse relaxed lovely and quickened up very well.
"Ryan (Moore, on Carlton House) got a split on the inside and I just had to come around Johnny (Murtagh, on Big Blue Kitten) but once he could see the horse on his inside he was never going to be beat.
"I just wanted to get him into a rhythm and get him relaxed, he has loads of class and can quicken and when things work out he's an exceptional horse."