Pacemaker Shining Copper blazed a trail but his race was run with half a mile still to travel, and Frankie Dettori made his move on the John Gosden-trained colt at that point.
However, Ryan Moore was sitting in his slipstream on Aidan O’Brien’s Found and despite Golden Horn battling hard once headed by the filly, the winner stuck to her guns and flashed past the post with a slender advantage.
Found – only the third filly to win the race after Pebbles and Miss Alleged - had endured a luckless run behind Golden Horn in the Arc, having been second to Gosden’s star in the Irish Champion Stakes and occupying the same position at Ascot on Champions Day.
O’Brien said: “She’s a very special filly, when you think she has run in two Champion Stakes and an Arc, and now this.
“To do it all in a month is remarkable. She was drawn badly in the Champion Stakes (at Ascot), and although she came out of it well, I thought the lads’ decision to come here was a little bit far fetched to be honest, but she didn’t have any luck in any of her races.
“I take my hat off to them for running her.
“At the start of the season, I did think she was the one for the Arc, but today she has more than made up for that and Ryan has given her a super ride.”
He went on: “Found will stay in training and obviously is very exciting to look forward to. Not many people noticed at the finish of the Arc that Ryan was almost stood up in the irons.”
Moore said: “She is very tough filly. To run in the Champion Stakes and the Arc and to come here is amazing. She beat a champion and that is special, too. I had to go around one and then I had to go.”
Coolmore partner Michael Tabor said: “At the beginning of the season Aidan was adamant this was our Arc filly. She didn’t get the rub of the green, but with Aidan when he says something it always comes right in the end.
“When Aidan says something eventually it will happen as he knows the difference.”
Also the winner of the Coral-Eclipse and Dante Stakes, Golden Horn heads for stallion duties having suffered just two defeats in his nine-race career – both to fillies, with his other reverse coming behind Arabian Queen in the Juddmonte International at York.
Connections were left to wonder what might have been had the Kentucky track not been hit by a deluge of rain through the early part of the week.
Dettori said: “I was happy where I was, but he couldn’t pick up on that ground, in fact he laboured on it.
“He ran a great race, though. He was labouring from the top of the stretch.”
Gosden added: “We always knew we were taking a risk running on ground like this that is softer than anything he’s run on before.
“It was too loose for him, but full marks to the filly for beating us fair and square.
“I said to everyone beforehand that after all the rain and three inches of it it would be far from ideal and the winner is bred to enjoy it more than us.
“Frankie said he was spinning his wheels all the time, but he appears to be bright after his race.
“It has been a long year and thank God we have had a European one-two.
“Our horse has run a terrific race on ground that didn’t suit him.”
Owner Anthony Oppenheimer said: “I’m very proud of our horse today. He’s lost nothing in defeat.”