Kyprios gave trainer Aidan O'Brien a record extending eighth Ascot Gold Cup on Thursday with Stradivarius missing out on a record-equalling fourth victory finishing a gallant third.
Frankie Dettori, on Stradivarius, had been shadowed and penned in on the rails by Kyprios's rider Ryan Moore throughout the race.
However, Moore was better placed to launch a challenge down the straight and got first run on Dettori and his rivals.
As Moore took the lead, pursued by Rossa Ryan on Mojo Star, Dettori had to bring Stradivarius widest of all using up precious ground and by the time there was a clear run the front two had gone.
Although Stradivarius made up ground it was too late and Kyprios was a worthy winner whilst Mojo Star had to make do with second as he had to in last year's Derby and St Leger.
For Stradivarius this was his final chance of equalling the O'Brien-trained Yeats's record (2006-09) as he will retire later this season.
Dettori was philosophical in defeat -- more so than a year ago when he had finished fourth and been criticised for getting himself trapped on the rails.
Stradivarius still returned to resounding applause round the parade ring as he had been prior to the race.
"He ran good but I had nowhere to go and had to go to the outside," said Dettori.
"That cost me but I don't think he would have won.
"He has been a good hero, he has been magnificent for racing and a brilliant horse. He just got beat today, he tried and went down fighting."
Dettori looked a good deal happier than Moore despite the latter being the victorious jockey.
"It was not the nicest race to ride in," said Moore, who was winning the race for a third time.
"I had to move him to the outside which I don't like doing but I had no option.
"This was not a true test and I don't think you saw the best of him."