Douvan's winning run came to a shuddering halt as Special Tiara claimed victory in the Betway Queen Mother Champion Chase, the feature race on day two of the Cheltenham Festival.
All eyes were on the Willie Mullins-trained Douvan, the brilliant seven-year-old who had won 14 races on the spin and was sent off the 2-9 favourite.
But after having jumped a little too exuberantly in places, he looked in serious trouble two fences from home - and so it proved.
Whereas Douvan retreated, eventually finishing down the field, the front-running Special Tiara (11-1) kept up an honest gallop under Noel Fehily and gamely fended off Fox Norton by a head.
Fehily, who won the Champion Hurdle on Tuesday, said: "Unbelievable. He's such a great ride, he's everything a two-mile chaser should be. He's a very good horse.
"I didn't so (beat Douvan), but I thought I had a great chance of being second. I got over the last and was surprised something hadn't come to me, but I knew he wasn't stopping.
"He has one way of running and that's flat to the mat and jump - I just let him get on with it.
"I've always loved two-mile chasers, the Champion Chase is the one you want to win. To win it is fantastic."
Winning trainer Henry de Bromhead said: "It's an amazing day, I'm just so pleased for everyone involved.
"He seemed in great form coming into it, but it was hard to believe (could win) with Douvan and everything else - Douvan had looked so good.
"For our lad, he just tries his heart out and no-one deserves it more.
"I thought he jumped the slickest he's ever jumped. Often he jumps a bit high. Incredible.
"Any day you win a Grade One at Cheltenham is just an amazing day."