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 years ago, who was also the runner-up 12 months 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.
Junior was rousted to get to the front but was harried all the way by Champion Court with Long Run perfectly placed just behind.
Six fences from home, Champion Court and Long Run appeared to have the field at full stretch in the three-mile heat run in the rain and testing conditions.
Champion Court put up a great performance until his stamina finally gave way in the straight.
Just as Long Run looked like he was going to have things all his way, Richard Johnson produced Captain Chris to put up a stern challenge.
Although Philip Hobbs' revitalised performer led after the last, Long Run came back for more to gain a narrow success.
Grands Crus was 14 lengths away in third place with Champion Court fourth.
"That was racing at it's best for me. I can't put it into words. It's an honour and a privilege" - Sam Waley-Cohen
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 it's 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.
He said: "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."
Henderson continued: "We had it in our minds that Bobs Worth would run in the Cheltenham race in January (Argento Chase), leaving Long Run free to run in the Denman (Aon) Chase at Newbury, but we'll have to discuss things with connections.
"I'd love to see Long Run back on better ground and I'm so pleased Sam and the horse have proved a point to people today."
Jockey Richard Johnson said of the runner-up: "I thought coming to the last I was going to win, but the other horse is a proven Gold Cup winner and he's just outstayed me.
"It was a great run and I'm just looking forward to riding him on better ground."
Scudamore said of third-placed Grands Crus: "He ran a great race and I'm most pleased he looks a lot more like his old self."