The Tim Easterby-trained five-year-old is now pencilled in for the King George Qatar Stakes at Glorious Goodwood and the Coolmore Nunthorpe Stakes back at the Knavesmire next month after this Listed triumph.
Copper Knight (2-1 favourite) was always close to the frenetic pace set by Caspian Prince before asserting in the final furlong and holding the pack, led by Dark Shot, by half a length under David Allan.
"Brilliant. What a lovely horse he is. He's been a star for us," said Easterby.
"Ideally he likes a bit more juice in the ground, but he copes with anything.
"A good race, that was. It was close at the finish, but he looked to be in command. He sticks his neck out.
"He'll probably run at Goodwood and possibly come back here for the Nunthorpe. He had to win this to pay for his entry fees!
"He's just a wonderful little racehorse."
Allan completed a quick double with a thrilling success on Red Verdon in the John Smith's Silver Cup.
He gave Ed Dunlop's six-year-old a patient ride as Weekender and Kelly's Dino took the field along for the majority of this mile and three-quarters contest.
They gave way a furlong out and Red Verdon (20-1) dug deep to lift the Group Three staying prize by a head from Gold Mount, with Raheen House a short head away in third.
Allan said: "My instructions were to take my time on him and not get involved early and get there in the last furlong. It couldn't have worked any better.
"I was picking the right horses to follow. No-one was going better than I was.
"He's been running in better races and I think he enjoyed the fact he could travel better.
"He dug in really well at the finish, was headed and got back up.
"He looks the type for the Ebor, but I'm hoping to get Wells Farhh Go for that. This track and a strong gallop in the Ebor would be ideal for this horse. You never know - I'll leave it up to them."