Winner of the 2017 Triumph Hurdle, Philip Hobbs struggled to get Defi Du Seuil back to anything like that level last season and after two poor runs decided to draw stumps.
He showed little of his old enthusiasm on his chasing debut at Cheltenham, and jumped stickily again early on in this assignment before warming to his task under Barry Geraghty.
Tom George's Black Op - with Sam Twiston-Davies standing in for Noel Fehily - jumped fine in the main but had to settle for third, while his fellow 6-4 joint-favourite Topofthegame ran an extraordinary race in second.
The Paul Nicholls-trained latter shied away from the tape at the start, conceding around 20 lengths before working his way into contention, and those exertions took their toll after the last.
Defi Du Seuil bounded clear from the final fence to win by three and a half lengths at 9/1. White Moon was the disappointment of the race, dropping away tamely in the straight.
The winner is owned by JP McManus and his racing manager Frank Berry said: "He probably got a fright at Cheltenham, looking at the way he jumped some of the fences there.
"He was a bit careful in the first mile today, but he ended up doing it really nicely. It looked a good race on paper, maybe one or two didn't perform, but you'd have to like the way he came home and the way he jumped the last four or five.
"That was over two-three, but he wasn't stopping - two and a half miles will be no problem. It's a nice problem to have deciding what's next, you could only be happy with him."
Sky Bet cut Defi Du Seuil to 14/1 from 33s for the Racing Post Arkle and introduced him into their JLT market at 10/1. Racing PR Manager Michael Shinners said: "It looked a hot race beforehand and lived up to the billing. Defi Du Seuil was much more polished over his fences last season and it was good to see him back to winning ways and once again look an exciting prospect."
