Frankie Dettori rode Undrafted to victory in the Diamond Jubilee Stakes to pick up his third Royal Ascot win.
The 44-year-old won on the American-trained 14-1 shot ahead of joint-favourite Brazen Beau.
"I didn't want to kick too soon," said Dettori. "Every time this horse runs, it finishes strongly. I saved for the last bit and it proved me right."
Dettori claimed his 50th career Royal Ascot win on Wednesday with victory on Osaila in the Sandringham Handicap.
He also won the Tercentenary Stakes at the festival on Thursday, before his third victory on Saturday.
Undrafted trainer Wesley Ward told Channel Four: "My man Frankie Dettori is the greatest, he is unbelievable.
"The horse is in peak form and condition but you have to have the right pilot. Hats off to him."
Horse racing correspondent Cornelius Lysaght
"America beating Australia and Britain: just the result officials yearned for when they started the push for runners from outside Europe to make Royal Ascot a truly global event.
"The international challenge has worked particularly well in the big sprints.
"Dettori's golden summer continues, and he joked that three wins usually wins the top jockey title, but Ryan Moore had other ideas.
"No success on day five for the record-breaker, but his week's been astonishing prompting one colleague to 're-name' it 'Ryan Ascot'. Spot on."
|Dettori's winning run|
|6 June: Wins the Derby at Epsom on Golden Horn|
|14 June: Completes Classic double with Star Of Seville in French Oaks|
|17 June: Records 50th career Royal Ascot victory aboard Osaila|
|18 June: Wins the Tercentenary Stakes at Royal Ascot on Time Test|
|20 June: Rides Undrafted to victory in the Diamond Jubilee Stakes at Royal Ascot|