The 6-4 favourite Might Bite held on in an exciting finish to win the King George VI Chase at Kempton Park.
Nico de Boinville's mount, who has been known for his quirky nature, was at the head of affairs throughout the race.
But although he led going over the final fence, the pair still had to work hard on the run-in.
Double Shuffle (50-1) chased all the way for a superb second under Adrian Heskin while Tea For Two (20-1) was third for jockey Lizzie Kelly.
The win gave trainer Nicky Henderson a big-race Kempton double after Buveur D'Air triumphed in the Christmas Hurdle earlier on the Kempton card.
There was also a first Grade One victory for Bryony Frost on the Paul Nicholls-trained Black Corton (4-1) in the Kauto Star Novices' Chase - she emulates Kelly, who achieved the feat on Tea For Two in the same race in 2015.
"I live for sitting on the back of a horse and he's my hero," said Frost afterwards. "The horse travelled nicely and Paul (Nicholls) told me he jumps well so don't change tactics.
"This race is so linked to Paul but I hadn't even remembered it was a Grade One - it's amazing."
King George winner Might Bite had fallen in the Kauto Star Novices' Chase at this meeting 12 months ago but Henderson was thrilled with his performance this time around.
"He was great, wasn't he? He jumped beautifully all the way and he enjoys doing that - he's so exuberant," he said.
"He has so much presence and charisma. You can't help but love him as he's gorgeous. He loves to show off, and that's what he was doing most of the way."
De Boinville added: "He was fantastic. On a horse that jumps as well as him you can't keep taking him back.
"He's given me a great spin and I couldn't be more delighted for the team.
"He jumped the last as if he had plenty left and I think he was just idling slightly. If something had come at him I think he'd have gone again.
"He's a delightful horse. I was a bit worried about the ground, having ridden on it earlier, but this was great. I must thank the guvnor and the owners for letting me ride him."
Buveur D'Air, the 2-11 favourite in the Christmas Hurdle who won March's Champion Hurdle at Cheltenham, was challenged by The New One at the second-last flight.
Barry Geraghty's mount jumped the last strongly and went on to win by two and a quarter lengths.
Cornelius Lysaght, BBC horse racing correspondent on the King George VI Chase
Sceptics will doubtless tut at the close proximity of two outsiders, but the runner-up relishes Kempton, and the third is a Grade One winner, coming back to form.
Plus, a whole lot of quality performers were scattered behind them.
What's more, the soft going didn't play to Might Bite's advantage at all.
He certainly threw down the gauntlet for the Gold Cup, showing no wayward tendencies, though Cheltenham, where, infamously, he dived for the gate to the stables after the final fence of a race in March, does present different problems - here, the stables gate is after the finishing line.