Imperial Monarch was out of luck for the Aidan O'Brien team as Saonois claimed a rough renewal of the Prix du Jockey Club at Chantilly.
O'Brien and his son Joseph were bidding for a Derby double following the triumph of Camelot at Epsom on Saturday.
But Imperial Monarch was last turning for home after being shuffled back and although he picked up well once switched wide in the home straight, his late flourish was not enough to get near the leaders.
The honours went to Saonois, trained by J-P Gauvin and ridden by Antoine Hamelin. Saint Baudolino claimed the runner-up spot in a bunch finish for the places.
The British raiders failed to make their presence felt, with Roger Varian's Ektihaam and Brian Meehan's Most Improved meeting all sorts of traffic problems. John Gosden's Gregorian was also well beaten.
French Fifteen, second to Camelot in the 2000 Guineas at Newmarket, was another who never had any chance as he found himself behind a wall of horses in the straight.