Fonteyn defied odds of 16-1 to land the Group One Royal Bahrain Sun Chariot Stakes at Newmarket.
The Kevin Ryan-trained filly was largely overlooked ahead of the contest but raced strongly in the inside rail when powering down the Rowley Mile under Neil Callan.
Passing the post three-quarters of a length ahead of John and Thady Gosden’s Laurel, the third-placed horse also came from the same stable in the shape of Grande Dame.
Saffron Beach was sent off the 6-4 favourite for trainer Jane Chapple-Hyam, but she came home eighth of the nine runners.