Jockey Bryan Cooper was in a dreamland after springing an upset aboard Benefficient in the Jewson Novices' Chase.
The 20-1 chance outstayed hot favourite Dynaste, ridden by Tom Scudamore, in the closing stages to score by three and a quarter lengths and leave the packed stands at Prestbury in a state of shock.
After making the running, Benefficient was headed by the strong travelling Dynaste and then Captain Conan turning into the home straight.
It looked like Dynaste would reward trainer David Pipe's decision to switch him from the RSA Chase, but he failed to go clear as expected and Benefficient swept by under Cooper to claim the spoils and earn a quote of 16-1 for next year's Betfred Cheltenham Gold Cup.
Cooper said: "I've been dreaming of this – it's a shock. He's such a tough horse and he's done so much for me, giving me my first Grade One winner and now my first Cheltenham Festival winner.
"We went a nice gallop and we never missed a fence.
"We were headed turning in, but I let him fill his lungs up and when I asked him to go on again he picked up."
Co-owners Aidan Shields and Niall Reilly said Cooper had carried out his instructions perfectly in dictating terms on Benefficient and then saving something for the home straight.
Reilly said: "I've been coming here for a good few years and Aidan has been coming for 20 years and you never dream of things like this happening.
"We've had winners here and there, and I said to Aidan that this horse was going to earn some respect today.
"People have said he's been lucky in the past but we knew from our trainer that this horse was going to have a big day."
Martin said he wasn't worried when Benefficient was overtaken because he knew Cooper was trying to conserve his energy for the closing stages of the race.
Optimistic about Benefficient's chances beforehand, he was pleased the pre-race tactics had paid off as well as he had hoped.
"Before the race I was nervous because I thought the horse had a live chance," he said. "The only horse I was worried about was Dynaste and that if luck was in our favour he couldn't be out of the first three."
