Immortal Verse won the Coronation Stakes at Royal Ascot as a French family affair spoiled home hopes.
Gerald Mosse brought his mount from last to first to land the Group One contest for trainer Robert Collet, whose son Rod trained the runner-up Nova Hawk.
The 8-1 chance Immortal Verse swooped round the outside of the field to win by two-and-a-quarter lengths from the 9-2 shot Nova Hawk.
Barefoot Lady (16-1) was best of the domestic runners, half a length further back in third for trainer Richard Fahey.
The Aidan O'Brien-trained Together, second in both the English and Irish 1,000 Guineas, did not run to that form and finished back in fifth.
Straight after the race, Collet Senior, speaking through an interpreter, told BBC Two: "My filly is easy, the best filly I've trained.
"At Newmarket in the 1,000 Guineas she wore a blind to go into the stalls and it irritated her, in the French Guineas things didn't go to plan and you forget that. Now she has proved she is a genuine Group 1 filly."
Mosse showed all his renowned cool as he let his mount, a winner last time out at Chantilly, settle at the rear of the field while Irish challenger Claiomh Solais set off in front.
As the race unfolded, Nova Hawk - who was fourth in the English and French Guineas - made her move under Stephane Pasquier.
But Mosse had taken Immortal Verse to the edge of the pack and swooped in the final furlong to ensure the first French-trained winner of the 2011 royal meeting.
She is the fifth French-trained filly to win the Coronation Stakes since 1989, with the last success coming when Banks Hill won for Andre Fabre in 2006.
Mosse added: "I hit the front a bit too fast, I was coming really easily but I had the race won from about 500 metres out. She has a fantastic turn of foot, she's really a great ride and I'm very pleased."
Immortal Verse's win was virtually replicated by Beachfire in the Wolferton Handicap in the next race when William Buick brought the bottom weight from last to first down the straight, John Gosden's four-year-old coming to life when faced with a wall of horses.
He drew smartly clear of Lost In The Moment to win going away by two-and-a-quarter lengths, with Waydownsouth a further length away.
The 6-4 favourite Green Destiny never got involved at any stage.
It was a second win of the day for Gosden and Buick, after Nathaniel underlined his promise ahead of the St Leger with an authorative display in the King Edward VII Stakes, revelling on the fast ground to kick clear down the straight and beat the staying-on Fiorente by five lengths.
Gosden, on being told Nathaniel had been installed as the new St Leger favourite, said: "It's the last Classic so we have to start thinking about it.
"He loved the ground and stayed well. He gets very fizzy and warm, that's his nature, but the jockey [William Buick] pointed him in the right direction."
Far more competitive was the Queen's Vase, a race that saw 7-2 favourite Namibian stay brilliantly to hold off a late charge from Solar Sky to win by a head.
The two were well clear of the rest of the field in a titanic battle down the straight, but Namibian held on - though he had to await the results of a stewards' enquiry after the front two came together near the line.
Eternal Heart finished third and Regent Street was fourth.
In the first race of the day, Jamie Spencer rode Samitar to victory in the Albany Stakes ahead of Inetrobil and Illaunglass.
"It's great to have a winner at Ascot," said trainer Mick Channon. "It's not easy to win here.
"The horses are running very consistently, we just needed to win. I believed in this filly, and this was the plan. As for the 1,000 Guineas, it is such a long way, and she's just a shell of a horse at the moment."
In the final race of the day, Manassas secured victory in the Buckingham Palace Stakes ahead of Excellent Guest, Striking Spirit and Decent Fella.