Sanctuaire made all the running to win the bet365.com Celebration Chase at Sandown.
Daryl Jacob gave his mount (9-2) a positive ride and the Paul Nicholls-trained runner jumped superbly to win by 17 lengths.
Henrietta Knight's Somersby (11-4 favourite) stayed on best of the rest to take second place under Dominic Elsworth, with David Pipe's Dan Breen (10-1) back in third for Tom Scudamore.
Jacob told Channel 4: "He jumped from fence to fence and I got a great spin off him.
"I had a chat with Ruby (Walsh) this morning and a good chat with Paul (Nicholls) and Ruby told me how to ride him and he said this horse is the expert."