Dinaria Des Obeaux justified odds-on favouritism in the Winning Fair Juvenile Hurdle at Fairyhouse after a stewards' inquiry.
Gordon Elliott's charge was sent off at 10-11 for the Grade Three contest and was at the head of affairs for much of the race, though Ex Patriot swept ahead approaching the last in the hands of Davy Russell.
Bryan Cooper was forced to switch Dinaris Des Obeaux out as Ex Patriot cut across her, and was gaining with every stride heading to the finish, missing out by a head.
The stewards then deemed the interference caused by Ex Patriot to be enough to reverse the placings, giving the win to Elliott's mare.
Elliott said: "She's a grand, honest mare that stays. She definitely got impeded and it's unfortunate for the connections of the second. We got a bit of luck today, but they are two nice horses.
"I wouldn't say it was the strongest race in the world, so I don't know whether she'll be going to Cheltenham."
Speaking before the demotion of her 5-1 chance, Ex Patriot's trainer Ellmarie Holden said: "That was unbelievable, absolutely super. It's his third run and he just keeps improving every time.
"He's just enthusiastic about the whole thing and loving it. He's getting sharper every time with his jumping.
"I wasn't too disappointed at Leopardstown as he still ran very well for his second run.
"We'll decide during the week now about Cheltenham. We'll see how he comes out of it.
"Davy said he was super and said the trip and ground were perfect.
"He seems to go on that ground. On his first run we were a bit concerned because we thought he might like nicer ground, so nicer ground wouldn't worry us either."