Cachet made every yard of the running to win the Qipco 1,000 Guineas at Newmarket for rookie trainer George Boughey.
It was a second Classic of the weekend for jockey James Doyle coming 24 hours after he steered Coroebus to success in the 2,000 Guineas.
Cachet, who won the Nell Gwyn at the Craven meeting, was sent off a 16-1 shot but led from the stalls and was never headed – despite the strong late challenge of Prosperous Voyage.
Cachet held on by a neck, with Tuesday another length and three-quarters back in third for Frankie Dettori.
Boughey said: “It's a very special day and I've got a lot of people to thank for getting here, but most notably the filly.
"She's been a superstar since she walked into the yard. It was always going to be the question, that long final furlong, but she's a star.
"It was a peach of a ride from James and she's held on."
Doyle said: “I promised I wouldn't get emotional today but that was incredible.
“I rode her a couple of times last year, to a Group One place in the Fillies' Mile, and we were talking about it beforehand, myself and George – she seems to be much stronger this year.
"That last half a furlong took forever and I was praying for the line, but she's all guts, she loves this track."
He added: "A special thank you to George, it's a young, growing team and he's doing amazing things - I think he's a name we're going to be hearing a lot about in the future."
On what is next for Cachet, Boughey said: "I think she'll probably go to (Royal) Ascot (Coronation Stakes).
"There's the Irish Guineas and the French, but I think she'll just go straight to Ascot."
