Bluestocking gave coach Ralph Beckett and jockey Rossa Ryan their largest win with victory within the Prix de l’Arc de Triomphe at Longchamp.
The four-year-old had been added to the sector at a price of £100,000 by owner-breeders Juddmonte after her spectacular win within the Prix Vermeille on the Paris observe final month.
The filly, who went off at 5-1, tracked the Aidan O’Brien-trained Los Angeles and Ryan Moore from the beginning.
She dug deep to complete strongly and maintain off runner-up Aventure, with Los Angeles third, to land a file seventh win in Europe’s richest race and £2.4m prize cash for the late Khalid Abdullah’s racing operation.
“She is a unprecedented beast,” Beckett advised ITV Racing.
“The draw helped. Rossa bought her in the fitting place – all the pieces went to plan and that is our best-ever day.”