Native River, ridden by champion jockey Richard Johnson and trained by Colin Tizzard, won the Cheltenham Gold Cup after beating 4-1 favourite Might Bite in an almighty duel between the two on Friday.
The eight-year-old 5-1 shot led from the start in what turned into a two-horse race, with the rest well beaten.
The pair were neck and neck as they leaped the final jump before Native River, who came third last year, won a sprint to the finish.
Anibale Fly (33-1) finished third in the flagship race of the four-day meeting.
“I’m speechless, he’s been a fantastic horse for me and I was lucky to pick up the ride on him. He’s just amazing,” said Johnson, who won the Gold Cup with Looks Like Trouble in 2000.
“He jumps for fun. I was getting squeezed, but at the second-last and the last he just wanted it so much. Eighteen years feels a long time ago now.”
Tizzard told ITV sport it was an unreal feeling to see Native River become the first to win at the second attempt: “Watching the Irish winning everything for the last three days, we thought we’d got no chance,” he said.
Second place was a disappointment for Might Bite’s trainer Nicky Henderson, who had been hoping to become the first to win the Gold Cup, Champion Hurdle and Champion Chase at one Cheltenham Festival.
Last year’s winner Sizing John was absent after suffering a fractured pelvis. It was the third year in a row the champion has missed the race after Coneygree and Don Cossack did not defend their crowns.