French star Cirrus des Aigles has had his fourth Prix Dollar taken away by stewards at Longchamp on the first day of the Prix de l'Arc de Triomphe meeting.

The eight-year-old, winner of six Group One races, fought back after being headed to regain the lead from Factional in the dying strides of the Group Two race.

However, the stewards ruled Cirrus Des Aigles, who is a gelding which bars him from racing in the Arc, had obstructed Planetaire who finished fifth.

Factional, trained by Andre Fabre, was awarded the race to give jockey Raphael Marchelli his first Group race winner while Cirrus des Aigles was demoted to fifth.

Cirrus des Aigles' trainer Corine Barande-Barbe was still delighted with her old warrior's performance after a long lay-off because of injury.

"He proved he is the best as he was yesterday and as he will be tomorrow," Barande-Barbe said.

"I was so impressed by his courage and the way he performed after being off for such a long time. Now it is on to Ascot and try and win a second Champion Stakes."

Earlier Gregory Benoist, who until November last year had yet to win a Group One race, got the perfect boost ahead of riding Ectot in the Arc as he guided Auvray to win the Group Two Prix Chaudenay.

The 31-year-old Belgian, who chose Ectot ahead of unbeaten French filly Avenir Certain as his Arc ride, produced the winner halfway down the straight.

He overhauled the always prominent English runner Vent de Force to win comfortably for trainer Elie Lellouche and owner Gerard Augustin-Normand, who are also the trainer and part owner of Ectot.

Benoist said it was the perfect fillip ahead of the biggest challenge of his professional life on Sunday (Monday AEDT).

"Well everyone can see I'm in top form!" he said.