Dettori looked to be on course to repeat his ‘Magnificent Seven of 1996 but fell short on race five as Turgenev was caught by Biometric at the death,
The 48-year-old opened the day with Al’Ali in the Norfolk Stakes for Simon Crisford and followed that win up by claiming victory in the Hampton Court aboard Sangrias.
He made it three in the Ribblesdale Stakes on John Gosden’s Star Catcher and capped off an incredible afternoon in the Gold Cup on Stradivarius.
Trainer Gosden praised Dettori as he said: “This 48-year-old kid take this to another level, like a Wimbledon semi-final and final.
“He’s riding quite beautifully. He occasionally listens to me, but not too much.”
Stradivarius also created history by wining his seventh race on the spin.
The win looked unlikely during the race as Dettori found himself behind a clutch of horses before powering through the gap once it presented itself.
“What a horse, he got me out of trouble,” said Dettori.
“He’s the horse for the big occasion and people love him.
“It’s great for everyone connected with the horse – every time he runs he delivers.”
On failing to win the fifth race, Dettori added: “20 years ago I would have won that!
“He was 16-1 this morning, went off favourite and he gave me a great spin.
“I’ve had a good day so I’m not going to cry.”
Ascot’s official bookmaking partner Betfred breathed a huge sigh of relief, along with the whole industry.
Spokesman Mark Pearson said: “Frankie riding the first four and especially getting a tune out of Stradivarius in the big one was very costly.
“However every bookie is going to bed tonight relieved because if Frankie had done the unthinkable it would have been the biggest pay-out in bookmaking history.”