A race controlled for much of the way by Frankie Dettori and Lismore, the two-and-a-quarter-mile showpiece turned into something of a sprint and try as Alan King's long odds-on Trueshan might under Hollie Doyle, he could never quite get on terms.
The Henry de Bromhead-trained Lismore refused to buckle, either, but in a pulsating finish it was the Andrew Balding-trained Coltrane (9-1) and David Probert who had enough to score by a neck from Trueshan, with Lismore a short head away in third.
Balding said: "He's done us proud. He's had a long season and the worry is that at some stage he's going to cry enough but he was so tough there, he's so game.
"The slow pace wouldn't have suited him. He's won over two and a half miles at Ascot and we were a little worried about the ground as he disappointed the last time he ran on very slow ground. He's a star.
"He's a course and distance winner so next year's Ascot Gold Cup would have to be an option, but we'll just enjoy today."
Of Trueshan, King said: "I think he was remembering Goodwood (third in Goodwood Cup) as he was frightened to let himself down today, even though the ground is perfect. He's gone right, he's gone left and it was only in the last half-furlong that Hollie said he's actually let himself go.
"I've never seen him do that before. I think he was thinking it was going to hurt again. It obviously hurt him at Goodwood, although he seemed fine.
"We had a very hard race at Newcastle (Northumberland Plate) and then we've run him on ground that's quicker than he likes at Goodwood and I think it left its mark.
"I've got to speak to the owners, but personally I would say it's Ascot or nowhere. I'm not going to get him back (for the Prix du Cadran) in two and a half weeks, so we'll hope we get really soft ground at Ascot, otherwise I might put him away for the winter again.
"It's been a total mess of a summer for him. We've tried to keep him ready to go, we've been to Ascot twice and not run, we went to Goodwood and ran him and York was a no brainer (not to run) because the ground was rattling quick, but he still went up there.
"He came up here on Thursday and came back Friday, so it's not ideal. Coltrane probably did the same to be fair and I'm not knocking him at all."
He added: "People have criticised me all the way through about not running him, but I think you can see why."