Bellshill won the Irish Gold Cup by a short head at Leopardstown on Sunday, with the field reduced to just four runners because of the conditions.
Favourite Road to Respect was edged into second place as Ruby Walsh guided the Willie Mullins-trained Bellshill to an impressive victory.
"We had few runners but we had the quality runners," said Mullins.
Six of the 10 runners were withdrawn because of unsuitable ground, including Mullins' Al Boum Photo.
Meanwhile, English-trained La Bague Au Roi won the Flogas Novice Chase from Kaiser Black and Hardline.
Speaking about his Gold Cup winner, Mullins added: "Our fellow was great. He jumped brilliant and Ruby was great on him.
"We're very keen to take him to Cheltenham, he needed the run badly at Christmas."
Sean Flanagan on Road To Respect kicked into the lead just after halfway and appeared to have the advantage after a big leap at the last, but Walsh and Bellshill recovered to win on the line.
Bellshill is now in from 20s to 12-1 with some bookmakers for the the Cheltenham Gold Cup.
Cornelius Lysaght, BBC racing correspondent
Plenty of race-mares have been top-notch hurdlers, but La Bague Au Roi is looking like as good a female Grade One steeplechaser as there's been for a while.
She extended her unbeaten score over fences with some fabulous jumping, and though the runner-up briefly threatened a turn-up, she kept on well.
That's a first British winner at Ireland's Dublin Racing Festival, now in its second year, and should encourage more overseas challengers - although officials who saw a long list of non-runners because of good to firm in places going will be hoping for wetter winters in future.