Jubilant jockey James Doyle hailed Blue Point as an "unbelievable" horse after the five-year-old won the Diamond Jubilee Stakes to complete a Royal Ascot double.
After landing the King's Stand Stakes on Tuesday, winning that race for a second year, the Godolphin-owned horse triumphed in Saturday's showpiece race by a head from the fast-finishing Dream Of Dreams.
Kachy, who finished third, had set a rapid early pace, but Blue Point, trained by Charlie Appleby, took over at the front and the 6-4 favourite held on as Dream Of Dreams came barrelling up behind.
Doyle said: "That was pretty special. He gave me an unbelievable feeling.
"I said to Charlie after his last piece of work before the King's Stand that he's probably one of the quickest horses I've ever ridden and he certainly is that.
"It got a little bit hairy late on. The other day I was able to do things all by myself without any pressure but Kachy went off at a hell of a pace, and this fella is just so genuine, all he wanted to do was chase him down."
Choisir in 2003 was the last horse to win both Group 1 races at the meeting, and Doyle said the achievement by Blue Point "earmarks him as a real champion".
Defoe, the 11-4 favourite, fended off Nagano Gold to take victory in the Hardwicke Stakes, where last year's Derby winner Masar finished fifth.
Cape Byron landed the Wokingham Stakes to justify his 7-2 favourite status, while Daniel Tudhope - later aboard Dream Of Dreams - rode 25-1 shot Space Traveller to victory in the Jersey Stakes.
Pinatubo, another Appleby-trained horse, edged out favourite Lope Y Fernandez in the Chesham Stakes, while Cleonte was the 7-2 winner of the final race of the festival, the Queen Alexandra Stakes.