Hardy Eustace, a 33-1 outsider, sprung a major surprise by leading all the way to win the Champion Hurdle, the big race on the opening day of the three-day Cheltenham festival.
Trained by Dessie Hughes and ridden by Conor O'Dwyer, the seven-year-old proved too strong up the hill for defending champion Rooster Booster.
The grey finished second, five lengths adrift, after being sent off the 11-8 favourite. Intersky Falcon, an 8-1 chance, was third.
Victory was especially poignant for the connections after the death of jockey Kieran Kelly in August. Kelly, who rode Hardy Eustace to victory in the Sun Alliance hurdle at last year's festival, died in hospital after sustaining head injuries in a fall at Kilbeggan.
"I can't describe it, fantastic, especially with the Kieran situation, it just makes it all the more emotional," O'Dwyer said.
Hardy Eustace is the first Irish-trained winner of the race since the great Istabraq won the third of his titles in 2000.
Earlier, Ireland drew first blood when 7-2 favourite Brave Inca landed the opening race, the Supreme Novices' Hurdle, for trainer Colm Murphy and jockey Barry Cash.
The result, which landed a sustained gamble, was an early blow for bookmakers looking to recover their losses from last year's festival when a host of big-race favourites won.
Punters were not smiling so much in later races though, with 40-1 shot Maximise landing the Kim Muir chase for champion trainer Martin Pipe, who had earlier celebrated success with Well Chief.
Eight-times champion jockey Tony McCoy, sporting a thick plaster across his face as a legacy of a recent broken cheekbone, was called on to produce his renowned strength in a finish to guide Well Chief to a battling victory in the Arkle Trophy.
McCoy showed a rare moment of emotion - punching the air in delight after the 9-1 chance had narrowly defeated Ireland's Kicking King, ridden by last year's top festival jockey Barry Geraghty.
The last race of the day went to the JP McManus owned Creon, a 40-1 outsider, who pipped GVA Ireland at the post.