Having chased home Frankel in four Group 1 races, O'Brien decided to avoid another clash with the great one in the Sussex Stakes and head to France.
However, it was not a easy race, with nine individual Group 1 winners in opposition. John Gosden supplied two of those in Fallen For You and Elusive Kate, and it was the latter who tried to make all.
Cityscape loomed up as a danger, with Soumillon hard at work on Excelebration, but as they entered the final furlong, the Irish runner began to pick up and O'Brien's four-year-old was well on top at the line. Cityscape was just over a length away in second, with Elusive Kate just holding on for third from the fast-finishing Moonlight Cloud.
Ryan Moore had been due to ride Excelebration but was stood down by the racecourse doctor after a fall earlier in the day.
O'Brien was absent, but Tom Goff of Blandford Bloodstock said having spoken to Coolmore: "He is in the Moulin and the QEII and I think one or other, or both, is next on the horizon for him. He's in all the top mile races worldwide."
Soumillon said: "It was a fantastic chance ride to get. I feel very sorry for Ryan as he was telling me before his fall that he thought the horse would win."
Trainer Roger Charlton said of Cityscape: "We've been beaten by a plainly better horse here, but it was a brave effort and he galloped all the way to the line. We can't be anything other than pleased, and now anything is possible. Ascot [Champions Day] would be a target, depending on what Frankel does. If Frankel sticks to a mile and a quarter we would go for the QEII."
His rider James Doyle said: "I was lucky enough to be able to ease him out from the rail and give him a bit of room. I couldn't fault the ground and the horse felt good."
Alan McCabe said of Caspar Netscher: "What an absolute superstar. Couldn't be happier with Caspar if he'd won – he ran a blinder."
Elsewhere, Roger Varian believes Firdaws is ready once again to show the form which had her finish third in the Fillies' Mile last season.
The daughter of Oaks winner Eswarah has always been highly regarded, but in two starts this season she has come nowhere near to approaching her juvenile form. However, Varian revealed she had valid excuses for her first start at Newbury and was far more pleased with her effort at York most recently.
A trip back to the Knavesmire could be on the cards, although she also holds an entry in the Upavon Fillies' Stakes at Salisbury on Wednesday.
The trainer said: "She was very disappointing at Newbury first time out but at the time I had one or two running below-par, even though we were still having the odd winner.
"There's no getting away from it, that was a shocker but she's really come to herself now. She didn't run too badly at York, I think she would have been third if she hadn't been interfered with.
"We've given her the option of Salisbury this week, but I think she wants stepping up to a mile and a half so we might wait for the Galtres at York."
As regards today, Sir Mark Prescott's Medicoe (8.10) can defy a penalty at Wolverhampton.