Victor Ludorum showed a fine turn of foot to maintain his unbeaten record in the Qatar Prix Jean-Luc Lagardere at ParisLongchamp.
Carrying the royal blue silks of Godolphin, he was settled in midfield by Mickael Barzalona as Frankie Dettori set the early fractions on Alson.
He was asked to throw down his challenge approaching the final furlong and the son of Shamardal, sent off the 2/1 favourite, found a neat change of gear to cut down the leader and win with something to spare.
Armory, who tracked the pace, was close-up in third.
Andre Fabre - who also trains Middle Park winner Earthlight in the Godolphin blue - said: "I think he is really good, as he is a laid-back horse and has a fantastic attitude. He does everything easily. The ground was a big concern, as he is a light mover, but he handled it very well. Race after race he remains unbeaten and does everything easily. He could be a very good horse. We will aim for a Classic campaign and the French Guineas, I'd imagine."
He added: "He is not too big or small, he is a neat horse. We will have discussions with Sheikh Mohammed, as he has a good bunch of two-year-olds, but I'd imagine he will be aimed at the French Guineas and the Prix du Jockey Club.
"He is less precocious than Earthlight and is not a natural two-year-old like Earthlight and has less natural speed than Earthlight, but he would stay further than him, for sure."
O'Brien said of Armory, who was nine lengths behind Godolphin's Charlie Appleby-trained Pinatubo in the National Stakes: "He's a lovely horse who is progressing all the time. We thought he'd be happy with the step up to a mile and he seemed to run a good race.
"In a perfect world we would have preferred better ground as such a good moving horse. They went a steady gallop and then quickened, and we were just caught out for a couple of strides. The better the ground, the better it is, I would have thought, with him. I would imagine that he will keep progressing."