The Outlier, an 8-1 shot ridden by 3lb claimer Paul O'Neill, landed the featured Peter Marsh Chase by more than 12 lengths at Haydock Park.
The grey, trained by Venetia Williams, pulled away at the second last to give O'Neill his 15th winner of the season.
Turpin Green (11-2) was second with 14-1 shot Truckers Tavern third, while favourite Snakebite fell away as heavy conditions took their toll.
Long-time leader Irish Raptor's mistake at the fourth-last saw him drop back.
Neill said: "He loves the ground and he had good form over the course and distance last time.
"The wind was very strong and he started to run around a little bit. Once I got hold of him and gave him a couple of slaps he put his head down for me.
"He's a type who's been improving this season. He won a maiden chase at Folkestone a couple of seasons back.
"Heavy ground is important to him and hopefully he'll make a (Grand) National horse."
Afsoun, the 11-8 favourite ridden by Mick Fitzgerald, romped to a nine-length victory in the Champion Hurdle Trial.
"Ireland keep on winning the Champion Hurdle so hopefully we might give them something to think about now," said trainer Nicky Henderson.