Long Run won the totesport Gold Cup under a superb ride from amateur Sam Waley-Cohen to give trainer Nicky Henderson his first ever winner of chasing's blue riband.
He became the first six-year-old since Mill House in 1962 to land the prize and was sent off the heavily backed 7-2 favourite.
The race lived up to every expectation, and with half a mile to go the three former champions - Kauto Star, Denman and Imperial Commander - were all in the firing line line.
But Long Run had them in his sights and he jumped to the front at the last strode away up the run-in to score with plenty in hand.
Denman ran another gallant race to finish runner-up for a second consecutive year, while Kauto Star held off stablemate What A Friend for third.
The winning trainer said: "Sam gave him a beautiful ride there just a moment coming down hill that I thought he needed daylight. He rode a brilliant race - like a professional."
The gelding's owner Robert Waley-Cohen, a proud father of the winning jockey, said: "I can't describe how this feels. It's just total elation."
An ecstatic Sam Waley-Cohen said: "He's a whole lot better than I thought he was. That's a very special feeling and he's a very special horse.
"This is beyond my wildest dreams. I didn't think we were going to get there, but he picked up, and I think he still had a bit left.
"When he got there he saw the crowd and he wanted to stop and have a look. What a horse he is."
Long Run is a top priced 6-1 to win next year's Gold Cup.
That's an unbelievable price - if they will lay it you.
