Long Run got up in the final strides to collar Captain Chris and regain his crown in the William Hill King George VI Chase at Kempton.
Captain Chris looked like going two better places than last year when he came through to head the winner of two seasons ago.
However, Long Run, the 15-8 favourite trained by Nicky Henderson, rallied for amateur Sam Waley-Cohen, to get back up and score by a neck.
Grands Crus was 14 lengths away in third place, with Champion Court fourth.
The winning rider said: "He was so brave. I had to keep asking him - I asked him early and maybe I asked too much as he was tired but so brave.
"This is his fifth year of competing at this level and he means an enormous amount to us. That was racing at its best for me. I can't put it into words. It's an honour and a privilege."
Long Run is owned by Waley-Cohen's father Robert, who added: "He's come here four times now and won three Grade Ones and been second to Kauto Star.
"I wasn't absolutely sure that we had got back up but as I came down the stairs from the stand, I saw his name go up and that was fantastic."
Henderson was similarly thrilled to see his former Cheltenham Gold Cup victor return to winning form, saying: "It was a brave call to go on when he did and it was the right call to make.
"It was a battle out there today and not the best ground for any of them. He's young but has been doing everything right. You would have to say last year was a disappointment but he's been running good races all the time."