War of Attrition won the Cheltenham Gold Cup in spectacular fashion on the final day of the Festival.
O'Dwyer and War of Attrition won by two-and-a-half lengths
Conor O'Dwyer's mount (15-2) hit the front down the back straight on the second circuit and kicked on to beat Hedgehunter (16-1) comfortably.
Forget The Past (9-1) under Barry Geraghty was third with 4-1 favourite Beef or Salmon trailing in 11th.
"You dream about these things. I've always had a lot of faith in him," said winning trainer Mouse Morris.
"I have always said he is one of the best I have ever had and I think he proved that."
War of Attrition, owned by Ryanair boss Michael O'Leary, won by two-and-a-half lengths after the showpiece 22-fence 3m 2f chase, the blue riband event of National Hunt racing.
Grand National winner Hedgehunter was seven lengths clear of Forget The Past with France's L'Ami (10-1) fourth.
The result makes it the first-ever 1-2-3 for Irish horses in the Gold Cup, a fitting statistic for St Patrick's Day.
English racer Lord of Illusion led the 22-strong field around the first circuit, from Ollie Magern and One Knight.
War of Attrition (right) beat Hedgehunter in the Gold Cup
As they ran past the stands and headed out into the country on the second lap, Forget The Past took up the running with War of Attrition handily placed.
O'Dwyer took over from three out and as Ruby Walsh and Hedgehunter mounted their challenge, the seven-year-old War of Attrition took off and charged to victory.
O'Dwyer, victorious in this race on Imperial Call 10 years ago, said: "It was an easy ride, he pinged the last two fences when he just stood off and he loves racing.
"This is an emotional moment and we made the right decision to come here - it has paid off.
"He jumped super and we had a great run - I had to come wide but he is only a second-season novice so I didn't want to be too tight on him either.
"When I wanted to go he was able to go, which was a huge plus."
Willie Mullins, trainer of Hedgehunter, was delighted with the effort of his 10-year-old.
"I never thought I would be so delighted to finish second in my life but I am after the way mine have been running," he said.
"He jumped fantastic and ran a fantastic race. The pace was a bit strong in the first half mile but he warmed to it nicely and he will definitely go for the Grand National now."
Beef Or Salmon, a winner of eight Grade One races, has never won outside of Ireland and has now failed in four attempts in the Gold Cup.
War of Attrition led an Irish 1-2-3 in the big race
"I'm beginning to believe the people now. I wonder if we can have the meeting transferred to Leopardstown," said trainer Michael Hourigan.
"There were no excuses, he was off the bridle early on and he just didn't perform."
Elsewhere on the card, Detroit City led home Fair Along in a Philip Hobbs one-two in the JCB Triumph Hurdle.
Fair Along took the field along quickly early on and although Detroit City looked to be struggling at around halfway, jockey Richard Johnson kept pushing away and he was soon back on the heels of the leaders.
Detroit City collared the leader at the last and looked strong as the run-in as he had a five-length victory.
"Fair Along probably did set the race up for him," admitted Hobbs afterwards. "It wasn't the intention to have Fair Along as a pacemaker for him but it worked that way and probably helped Detroit City.
"He's a very genuine horse but he does badly need further than two miles and he was outpaced in the middle of the race. Richard really had to stoke him up.
"In the Triumph they go very quick and he needed something to sharpen him up a bit and the visor worked well. I was more than hopeful he would win."