Stradivarius ridden by Frankie Dettori became the first horse to win successive Ascot Gold Cups since Yeats won his fourth in 2009 on Thursday.
Dettori, who is on course to sweep the six race card having won all four races, had him in perfect position throughout the race.
Once the 48-year-old Italian extracted him from a little bit of trouble in the finishing straight and hit the front there seemed little danger to the John Gosden-trained star stayer.
Dettori performed his trademark flying dismount before modestly praising the horse -- who is on course for a second successive million pound bonus if he adds the Goodwood Cup and Lonsdale Cup at York.
"What a horse, he got me out of trouble," said Dettori.
Gosden, who had got off the mark for the week earlier when Dettori rode Star Catcher to victory in the Ribblesdale Stakes, said both horse and rider were exceptional.
"Full marks to a remarkable horse," said Gosden.
"He's an athlete and he's a charming horse to be around.
"This 48-year-old kid (Dettori) take this to another level, like a Wimbledon semi-final and final.
"He's riding quite beautifully."
Gosden and Dettori go back a long way and it was the Cambridge graduate trainer who offered him a way back after a wayward time which included a ban for taking cocaine.
Gosden, though, said sometimes his mentor-like approach goes in one ear and out the other.
"He occasionally listens to me, but not too much."
Both long time pacesetter Dee Ex Bee and rank outsider Master of Reality stuck to their task but they could not find an extra gear to overhaul Stradivarius.
Melbourne Cup winner Cross Counter had looked full of running coming round the bend but his challenge petered out and he finished fourth.