Master Irish trainer Aidan O'Brien plundered Sunday's French Oaks at Chantilly to add to his French Derby win a fortnight ago.
Joan Of Arc, ridden by Ioritz Mendizabal, supplied O'Brien with his first Prix de Diane run over the same 2100m course as stablemate St Mark's Basilica had negotiated to land the Prix du Jockey-Club.
Always prominent behind pacesetter Sibila Spain Joan Of Arc, a daughter of eminent stallion Galileo, was asked to quicken two furlongs out, hitting the front close to the line.
"I have to thank Aidan O'Brien for allowing me to ride such great horses, it's magic, unbelievable," said Mendizabal, for whom this was also a first French Oaks success after being the man on board St Mark's Basilica.
In second came the favourite, Philomene, ridden by Mickael Barzalona who was finishing like a train up the outside.