Silviniaco Conti gave trainer Paul Nicholls an eighth triumph in the William Hill King George VI Chase when outstaying Cue Card in the Christmas showpiece at Kempton.
Cue Card looked likely to win when he held a good lead early in the straight, but he emptied under Joe Tizzard between the last two fences.
That gave Noel Fehily the incentive on Silviniaco Conti (7-2) to grab Cue Card and go away after the last to win by three and a half lengths.
The winner's stablemate Al Ferof was third, 11 lengths away.
Cue Card made a tremendous effort to make all the running and put in a superb round of jumping.
He had all his rivals hard at work except for Silviniaco Conti, who exposed Cue Card's suspect stamina at three miles, especially under testing conditions.
Riverside Theatre and Champion Court both exited at the sixth fence, while dual winner Long Run went out at the last.
Fehily said: "I was slow over three out and I thought Joe had got away from me, but this horse is as tough as nails and he's a very good horse.
"This is a different track (to Haydock) and I knew my horse would be fitter today.
"Paul (Nicholls) has done a great job - he told me all week he'd improved from Haydock (when third to Cue Card in the Betfair Chase) and he has. It was brilliant.
"I've not ridden a Gold Cup winner, but I hope he's a Gold Cup horse. This is unbelievable."
Nicholls said: "That's brilliant. I knew if I had him at his best at Haydock he wouldn't win today.
"Sometimes you win these races with a horse like him, that if you'd have got to the bottom of him at Haydock he wouldn't have won today.
"It was heavy that day, the run brought him on enormously and I knew he'd stay. I said to Noel to make plenty of use of him.
"Kempton is not an ideal track for him a he jumps a bit out to the left, but he stays forever. All he does is stay, as you saw today. Better ground and a bit further will suit him well.
"Today was his target - last year the targets were the Charlie Hall and the Betfair. This year was a bit different, to come here and then go for the Gold Cup.
"You have to be a true stayer to win round here and though Cue Card won round Haydock it was different ground. He had a soft lead and I didn't want that to happen today.
"It's great to win this race with something different (previous wins were five with Kauto Star and two with See More Business). I thought we had a great chance in last season's Gold Cup, but it didn't happen "