Coneygree became the first novice to strike for 41 years when making most of the running in the Betfred Cheltenham Gold Cup.
The eight-year-old, trained by Mark Bradstock and ridden by Nico de Boinville, took the blue riband prize of steeplechasing on only his fourth race over fences.
The success fully vindicated the decision to bypass the RSA Chase earlier in the week and run in the Gold Cup instead.
Coneygree (7-1) held on up the hill by a length and a half from Djakadam (10-1), with Road To Riches (8-1) two lengths away in third.
De Boinville said: "It's the best feeling ever, I'm lost for words. I never thought they shouldn't have run in this, it was a great plan.
"The weather gods were looking down on us and the ground was ideal.
"He's so deceptive, even when he gets in tight he's brilliant, it's all thanks to the Bradstock family, it's a great family effort.
"I must thank the owners and the Bradstocks for keeping the faith in me. These horses only come once in a lifetime."
Sara Bradstock, wife of the winning trainer and daughter of the late Lord Oaksey, who bred Coneygree, said: "He (Lord Oaksey) is not here, but he's here in spirit.
"I'd been saying to people, when we win the Gold Cup we'll win the lottery, it's that amazing."
"It's only his fourth run over fences, but he had so much time off and he's wise in his own way."
Lady Oaksey said: "I've been asking myself what decision would John (Oaksey) have made? As it turned out, it was a very good decision after looking at Vautour and Don Poli (in the novice chases).
"To win this now - you dream and it's absolutely amazing."
Mrs Bradstock added: "All the people quoted stats at us, but this horse knows how to jump and how to gallop and he showed them.
"We were forecast real rain, which made the decision for us, and it was an open Gold Cup.
"It's so unbelievable, I've been in the yard from 6am until 10pm and it's all for this.
"All the big yards spend telephone numbers on horses and our mare cost £3,000.
"People were asking after Newbury (when Richard Johnson rode in the Denman Chase) if Nico would get the ride back, but of course he would - he rides him beautifully, he'll be a great jockey.
"It's a little bit back to work later as my favourite person, Carruthers, runs tomorrow (at Uttoxeter), but I might not be at my best!
"It shows anyone can do it, you don't need millions
"He didn't know he's a novice."
The winning trainer said: "I'm numb, it's wonderful. It won't sink in for a while, but it's great.
"We've done it before in smaller races and we'll still keep doing it, but it's fantastic to do it on the big stage.
"I can't remember where I watched it as I'm not very good at watching races.
"The decision was very tricky because the weather forecast was so up and down and obviously we were liaising very closely with Simon Claisse (clerk of the course) and walking the course. But we made the right decision.
"He's a gorgeous horse and it's so tragic that Sara's dad (Lord Oaksey) wasn't here today to see it."