Connections of Lord Windermere survived a lengthy stewards' inquiry to take glory at Cheltenham after the eight-year-old came from last to first to snatch victory in the Betfred Gold Cup.
Trained by Jim Culloty, who won three Gold Cups on Best Mate as a jockey, last year's RSA Chase hero just prevailed from On His Own after an amazing run to the line.
Silviniaco Conti led over the last, but he was collared by Davy Russell on Lord Windermere (20-1), who just held the Willie Mullins-trained On his Own (16-1) by a short head.
The Giant Bolster (14-1) stayed on strongly to finish third.
After two false starts, Knockara Beau was quickly away, although On His Own soon took it up while Lord Windermere was a few lengths detached in last place after a few fences.
Teaforthree and Lyreen Legend were others to join in with pace-making duties and then Last Instalment unseated his rider at the fifth-last fence.
Silviniaco Conti led three out and last year's winner Bobs Worth was also in with a chance as the pack closed in a wide-open race.
Lord Windermere joined in the fight late, but he veered right on the punishing dash to the line, resulting in an inquiry, as he just kept On His Own at bay.
An anxious wait followed before the stewards announced the placings would remain unaltered.
Russell said: "I can't believe it, I was never on the bridle.
"I was never in the race, the whole field was in front of me for the whole race, I had to sit and suffer the whole way.
"I didn't use any petrol, I went around the inside and he jumped great.
"The whole way round I was hunting, I thought the race had gone - the credit has to go to Jim Culloty, what a man."
Russell went on: "I was on the best horse in the race. He was very idle, like he was last year.
"Silviniaco Conti veered over and startled him a little bit.
"I wanted to do the right thing for the horse. I couldn't ride a winner for Jim all year, but he kept saying to me wait for Cheltenham."
Culloty said: "To be fair halfway round Davy Russell was getting the sack!
"He was beaten 26 lengths at Leopardsstown last month, but Davy said take no notice, it will be a different ball game at Cheltenham.
"I knew he'd take his time but that was waiting tactics exaggerated.
"I can't believe it. The horses just weren't right this season, but God they have come right at the right time."
Graham Wylie, owner of On His Own, said: "I just think my horse has run a fantastic race. I wasn't expecting to come here and win it. We knew there were good horses in the race.
"The way he battled up the hill, I was so proud of him."
Mullins said: "I thought he was interfered with and he was beaten a short head and was in front after the line.
"The stewards felt he didn't deserve to get it and what more can I do at this stage
"David (Casey) was disappointed at the outcome of the inquiry."
Asked if he might appeal, Mullins said: "I'll have a chat with the owners and see what they want to do. I'll have a chat with David and then speak to people who are more experienced than me on appeals in England.
"Four weeks ago he was just a handicapper going for the Grand National, then he ran a terrific race in the Bobbyjo and we said we'd go to Punchestown for the Gold Cup there, then I got home and thought why not go for the Gold Cup in England.
"I had a look at the supplementary fee and talked to Graham and he said yes.
"Coming here this morning if I thought we'd get second I'd have been delighted.
"He'll go back to Punchestown."
Meanwhile, Tiger Roll oozed class when scooting up the hill to win the JCB Triumph Hurdle.
Russell was back in the Gigginstown House Stud colours replacing the injured Bryan Cooper, and Gordon Elliott's youngster never looked in any danger as he travelled sweetly in behind the leaders.
He had Guitar Pete and Kentucky Hyden for company over the last, but Russell kicked him clear for a three-and-a-quarter-length win from the latter.
Ruby Walsh took a crashing fall on Abbyssial when leading early on and suffered a compound fracture of his right humerus, the bone in the upper arm. The rider was set to undergo surgery on the open fracture at Gloucester Hospital.
Very Wood sprang a huge 33-1 surprise in the Albert Bartlett Novices' Hurdle to put trainer Noel Meade back on the Cheltenham Festival roll of honour.
Meade, who had endured a miserable start to 2014, was without a win at the big meeting since Go Native landed the Supreme Novices' Hurdle five years ago.