Esoterique gave Andre Fabre a one-two in the Prix Rothschild at Deauville when quickening past her much-better fancied stablemate Miss France.
The Group One event boiled up into a very tactical renewal, with 1000 Guineas winner Miss France and Maxime Guyon looking to have made a decisive move inside the final furlong before Pierre-Charles Boudot swept past on the wide outside.
The only British runner in the quartet, the Sir Michael Stoute-trained Integral, had every chance but could only finish third.
No-one was particularly keen to go on, and they quickly split into couples with L'Amour De Ma Vie setting a laboured gallop on the far side, followed by her Duke Of Cambridge Stakes conqueror Integral.
The Fabre pair then elected to join them, and Esoterique was in last place but still travelling well.
The Danehill Dancer four-year-old, who is owned by Baron Edouard De Rothschild, had beaten Integral in the Dahlia Stakes at Newmarket in the Spring but was no match for that rival at Royal Ascot.
Boudot said: "It was great because I just completely switched her off and that is what she needs, she needs to be relaxed.
"I got a brilliant lead right up to the last furlong pole and when she quickens she really knows how to.
"She has a really good turn of foot and responded immediately."
Boudot was riding his second Group One winner having partnered Gallante to win the Grand Prix de Paris last month.
The Aga Khan's filly Ervedya had earlier extended her unbeaten record to three with a tidy victory in the Prix de Cabourg.
Trained by Jean-Claude Rouget, the daughter of promising first-season sire Siyouni had started her career at little-known Tarbes before stepping up in class at Maisons-Laffitte.
It was all rather easy for Thierry Jarnet, as he sat on the rail behind Mocklershill and a huge gap opened for him, with the experienced rider pushing Erevedya two lengths clear using just hands and heels.
The Group Three is often a warm-up for the Prix Morny back at Deauville in three weeks, for which Ervedya has an entry.