Cavalryman, trained by Andre Fabre and ridden by Maxime Guyon, won the Group One Grand Prix De Paris at Longchamp on Tuesday evening.
With the French capital joining the rest of the country for a national holiday to celebrate Bastille Day, the crowds turned out in large numbers in the west of the city.
Hail Caesar made the early pace for his more illustrious Aidan O'Brien-trained stablemates, with Age Of Aquarius tracking him in second under Johnny Murtagh.
The latter went on around three furlongs from home, with Frankie Dettori asking Godolphin's Mastery to engage top gear.
Murtagh was still in front two furlongs out but Cavalryman was just finding his stride and really impressed in the way he picked up, accounting for Age Of Aquarius and Mastery rather cosily in the end.
Hot favourite Beheshtam was a big disappointment and never seriously threatened on ground that was quicker than ideal.
‘I was quite confident coming into the race as he is a progressive horse by Halling and he has won nicely,’ the winning trainer said afterwards.
‘He is effective from a mile and a quarter on heavy ground to a mile and a half. He was beaten in a Group Two last time out by Cutlass Bay and they are the same type of horse.
‘I'm not sure about plans. I will have to talk to Sheikh Mohammed, and the same goes for Cutlass Bay who we have been saving for a soft ground autumn campaign.’
O'Brien said of Age Of Aquarius: ‘He ran a good race, he's a genuine, solid horse and fought on well.’
Trainer Saeed bin Suroor said of Mastery: ‘He ran well but has been beaten by a better horse on the day. I thought he might go close when Frankie asked him for an effort and he tried hard. He just wasn't good enough to win.
‘He was in a good position throughout the race and a mile and a half suits him well, but there is no plan at the moment.’