Kauto Star rolled back the years to win the Betfair Chase at Haydock.
Paul Nicholls' remarkable stable star was winning the race for the fourth time and was cheered around the parade ring beforehand.
He was always prominent under Ruby Walsh and produced a superb round of fencing, putting Long Run's own jumping under pressure.
The reigning Gold Cup champion cracked with mistakes at two fences down the back straight for the final time and Kauto Star set sail for home.
Long Run battled all the way to the line but could never get to the winner who scored by eight lengths and returned to an incredible reception.
Sky Bet reacted by cutting Kauto Star to 5-1 from 16s for the William Hill King George VI Chase at Kempton on Boxing Day with Long Run 6-4 from 10-11 for the same race.
The winner is 12-1 from 33-1 to win the Betfred Cheltenham Gold Cup for a remarkable third time.
Nicholls, who was enjoying a big-race double after the success of Master Minded, also owned by Clive Smith, at Ascot, said: "I'm speechless. That's the best day I've ever had. It's just amazing.
"We'd left no stone unturned, I'd got him as fit as he ever had been. We'd always thought about trying to make the running today, but hadn't told anyone for obvious reasons, and it all went to plan.
"Last year at home he always made a noise on the gallops and he wasn't finishing his races, but for some reason this year he's not making any noise at all.
"He's great for racing, and I hope those that said he should have been retired will apologise."
Walsh added: "He's an amazing horse. Paul had him spot on. I was hoping there would be another big day in him so I'm glad now I'm here and not at Ascot (riding Master Minded).
"I thought I'd take the bull by the horns and see how we get on. It's just a pleasure."
A proud owner Clive Smith said: "He's just as good as ever - he appears to be. It's such a wonderful win. Everyone was so excited.
"They cheered him before the race and they cheered him afterwards. It was fantastic.
"He knows he's king and he just said, 'here I am'. He's an amazing horse and he's such a wonderful, talented creature.
"I've always thought if he ran well today I'd like him to go back to Kempton as he has won it four times and deserves another crack."