Bad As I Wanna Be led home a British one-two in the Prix Morny-Casinos Barriere in Deauville on Sunday.
Brian Meehan`s juvenile took control over two furlongs out and ran out the comfortable winner from the John Gosden-trained Endless Summer.
Godolphin`s French-based two-year-old Noverre finished third for Evry trainer David Loder.
The Italian-trained Rolly Polly was fourth with Aidan O`Brien`s Pyrus - second to Endless Summer in the Richmond Stakes - fifth of the six runners.
Bad As I Wanna Be burst clear of the pack to win the six-furlong Group One contest at 15.4-1.
Endless Summer, the 11-10 favourite, was six lengths back in second with a further length back to Noverre.
Bad As I Wanna Be, unfancied by the locals after his minor win in a Windsor maiden, was very impressive in landing the #76,849 first prize.
Tucked in behind early leader Rolly Polly from Italy jockey Gerald Mosse asked him to quicken over two furlongs out and the response was immediate.
He lengthened like a potential champion in the rain-softened ground.
Mosse, recording his fourth success in the Morny, was clearly taken with the winner`s performance.
He said: 'He has lots of speed. I let them gallop early on and when I asked him to accelerate he reacted really well, he handled the soft comfortably.'
Endless Summer under Frankie Dettori, who had flown in from Chicago where he trailed in last on Slickly in the Arlington Million on Saturday night, was doing all his best work at the end but never looked like catching the winner.
Meehan was over the moon with Bad As I Wanna Be`s effort.
He said: 'I`m obviously delighted - it was a great performance. I wasn`t totally surprised. He`s a lovely horse and we`ve always thought a lot about him.
'He was disappointing at Newbury (11th of 13 on his debut). Whether the ground was too firm or what I don`t know maybe it was just one of those things but he bolted up at Windsor and has bolted up again today.'
There are no immediate plans for the son of Common Grounds.
'There is the Middle Park but we`ll just have to wait and see,' added Meehan. 'I suppose I`ll have to train him as a Guineas horse now.
