Supasundae claimed a dramatic victory after both Samcro and Melon came to grief in the BETDAQ 2% Commission Punchestown Champion Hurdle.
The previously unbeaten Samcro was the 5-6 favourite for Gordon Elliott, stepping out of novice company the first time, with the Willie Mullins-trained Melon widely regarded as his biggest threat after pushing Buveur D'Air all the way in the Champion Hurdle at Cheltenham.
Last year's winner Wicklow Brave, also trained by Mullins, cut out much of the running under the trainer's son, Patrick, and remained in front approaching the third flight from home.
Samcro and Melon, ridden by Jack Kennedy and Paul Townend respectively, were both making their move when they fell independently at the same obstacle.
From that point Robbie Power took dead aim at Wicklow Brave aboard Jessica Harrington's Irish Champion Hurdle winner Supasundae and the 7-1 shot powered clear for a decisive three-and-a-quarter-length success.
Wicklow Brave was a clear second ahead of another Mullins inmate Bleu Berry in third.
Power said: "I saw Samcro fall, I didn't know Melon had fallen, but if you don't buy a ticket, you don't win."
Harrington said: "Maybe we got lucky there, but he was going very well when the other two fell, and as soon as he got to the front, he started to pull himself up.
"He's had an unbelievable season, when you think of what he's done. He's a horse that went to Cheltenham, Aintree and finished second in both those places, and then on to win here.
"He has put in some great performances, he's a great horse."
Robbie Power speaks about his surprise win on Supasundae pic.twitter.com/fuPyUeDFYw— RTÉ Racing (@RTEracing) April 27, 2018