Kyprios held off Mojo Star and Stradivarius to claim the Gold Cup at Royal Ascot for Aidan O'Brien and Ryan Moore.
Having gone a slow pace there were plenty in with chances turning into the straight, as the mare Princess Zoe just about hit the front a furlong out looking to go one better than 12 months ago.
She was soon headed by Kyprios but Mojo Star, second in the Derby and St Leger last year, and eventually Stradivarius, having had to be switched for a run, threw down their challenge.
But it was not to be, as the 13-8 favourite held on for a famous win by half a length with another three-quarters of a length back to Frankie Dettori and Stradivarius, who was bidding to join the O’Brien-trained Yeats as a four-time winner.
"We're delighted with him, Ryan gave him a great ride," said O’Brien, who was landing the historic race for the eighth time.
"He’s a baby, but he’s a brave horse and he’s going to progress – he’s only a baby and he missed all of last year. We thought he would do the Leger, but he got out under the stalls ([n the Queen’s Vase] last year and badly bruised his back.
"We couldn’t race him for the rest of the year – he’s a brave horse and we think there’s more to come from him.
"It was a competitive race with Stradivarius and all the good horses. It’s incredible, and it was great Stradivarius was here and he ran in this race. It makes these races even more special and incredible. I’m delighted for all the lads and the team."
He added: "He could race for a good while, he's a lovely, kind, good-natured horse and a very sound horse.
"Hopefully the lads will decide to keep him going [next year]."
Moore, who was given a two-day ban for careless riding, said: "It wasn't a nice race to ride. Kyprios stepped slow for him which was unusual. I didn’t like the position I was in. I knew I had Frankie on my inside and they were going slow up front.
"I had to move him to the outside and I don’t like doing that, but I felt I had to keep Kyprios going.
"He’s got there and Mojo Star has come to us and this fella kicked in then and it was comfortable at the line.
"It wasn’t a true test today, I don’t think we saw the best of him. I’m glad he has come over here and won – there are plenty more good days to be had with him.
"He is brave. It was a more complicated race than it should have been. I think he was much the best."