Last season's Prix de l'Arc de Triomphe heroine Danedream bounced back to her best to beat Nathaniel in a bobbing finish to the King George VI And Queen Elizabeth Stakes at Ascot.
Nathaniel was attempting to defend his crown in the mile-and-a-half Group One feature, having made a winning return in the Coral-Eclipse at Sandown a fortnight ago.
He looked likely to land the prize when he quickened into the lead in the home straight, but the Peter Schiergen-trained Danedream (9-1) flew home in the hands of Andrasch Starke to prevail by a nose.
St Nicholas Abbey’s withering late run saw him get up for third place.
The John Gosden-trained Nathaniel was one of three horses who had battled for favouritism during the week.
And while he was settled in midfield by William Buick, main market rivals Sea Moon and St Nicholas Abbey were at the rear.
Nathaniel was the first one of the major players to go for home and when he hit the front it seemed as though he would deliver another Group One victory.
But Danedream, who had disappointed in the Grand Prix de Saint-Cloud on her latest appearance, was really motoring inside the final furlong and got up on the line to claim a famous triumph for her German trainer.
St Nicholas Abbey finished well from the back, another length and a half away, with French raider Reliable Man fourth.
Sea Moon, the 2-1 favourite, was further back in the field.
Winning jockey Starke said: "It was close - it was very tight - but I had a good feeling.
"It was exciting to come to race like this, and everything was in good shape.
"She fought hard and it's definitely the biggest moment in my life."
Schiergen said: "The last race there was no pace, but today there was a good pace.
"It's a good feeling. It's very important for Germany and it's very good for German racing.
"We'll go to Baden-Baden (Grosser Preis Von Baden) next and after that we'll go to the Arc."
Gosden said of Nathaniel: "I'm delighted with him. I didn't know which horse had won crossing the line and I was on the line.
"The winner has come back to her best. Anyone who was lucky enough to see her win the Arc last year, breaking the track record and destroying the colts, would know she is marvellous.
"She didn't handle the ground at Saint-Cloud the other day and she's come here and run a blinder, so full marks to her.
"Our horse has run his race quite brilliantly - I'm beyond thrilled.
"I can't believe in two weeks he can run two races like that back to back. It's quite impressive.
"I think I'll suggest that Danedream now goes to the breeding shed!"
Joseph O'Brien found himself in hot water with the stewards after the feature event, incurring a seven-day suspension (4-10 August) and a £900 fine for his use of the whip on St Nicholas Abbey.
The ban will keep O'Brien on the sidelines for the last day of Glorious Goodwood on 4 August.
Buick was also suspended two days (5-6 August) for having used his whip above the permitted level.