Illinois got Arc weekend off to a flying start for Aidan O’Brien and Ryan Moore with a determined victory in the Qatar Prix Chaudenay at ParisLongchamp.

Having filled the runner-up spot in the Grand Prix de Paris, the Great Voltigeur and the St Leger since his Royal Ascot victory in the Queen’s Vase, the Galileo colt was a warm order to strike Group 2 gold on his return to the Bois de Boulogne and was soon bowling along at the head of affairs.

Moore had to get to work from the home turn and the 4/9 favourite looked at the mercy of Trafalgar Square after being joined and briefly passed by his French rival, but Illinois gritted his teeth to keep himself in the fight and battled back to score by a widening two lengths at the line.

“I’m delighted, he’s a lovely horse and straightforward and stays very well. He’s lazy but finds plenty and Ryan said he’d have no problem coming back in trip if he needs to,” said O’Brien.

“In an ideal world you’d prefer to get a lead, but we’re very happy as it was a lovely race to come to after he got beat in the Leger.

“He should be a lovely four-year-old. I was obviously concerned when the other horse came to him, but knowing him he finds loads and Ryan gave him a great ride – that’s Ryan all over, isn’t it?”

O’Brien added: “That will probably be it for him for this year, I’d imagine. It’s a nice, long winter and he’ll be ready to start early in the spring. Ryan said he could start in Dubai or anywhere.”

The trainer saddled three runners in the Group 1 Prix de Royallieu later on the card and it was the outsider of the three, Grateful, who emerged on top under Christophe Soumillon.

By Galileo out of Group 1 winner Tepin, Grateful won at Group 3 level at Fairyhouse in July and had caught the eye when travelling well at Doncaster last time out, where she finished third in the Park Hill Stakes.

O'Brien and Moore had earlier won the Arqana Series Criterium d'Automne, a race restricted to Arqana Sale purchases, with Mount Kilimanjaro. The Siyouni colt cost €420,000 as a yearling and had shown promise on his first two starts, finishing fifth at Leopardstown and third at Newmarket.