Imperial Commander stayed on strongly up the final hill for trainer Nigel Twiston-Davies and jockey Paddy Brennan to land the totesport Cheltenham Gold Cup.
The 7-1 chance travelled powerfully all the way and with Kauto Star falling four fences out, only 2008 Gold Cup winner Denman could stay with him on the turn for home.
Imperial Commander was easily travelling the best of the two, however, and after going ahead on the run to the last, he powered away on the run-in to win with seven lengths to spare.
Reigning champion Kauto Star, chasing his third Gold Cup success, had already made a horrendous mistake at the eighth fence before he came down when looking beaten.
Brennan said: "It's by far the best day of my life. I'm speechless. It was a dream the whole way.
"I've just got to take time to thank my boss (Twiston-Davies). He's the best boss ever - he's produced two horses this week (Imperial Commander and Champion Hurdle runner-up Khyber Kim) and I just had to steer them."
Twiston-Davies added: "It's absolutely superb. I thought Kauto was in trouble some way out before he fell.
"All the hacks were saying he didn't stay, so we'll go for the Ryanair next year!
"It's just absolutely brilliant. It's been very hard for us sat there with the third-favourite when all the talk was about Kauto and Denman, but we always knew we were going to win."
