Ireland's hopes of securing a first Cheltenham Gold Cup in seven years were dealt a blow as great hopes Flemenstar and Sir Des Champs were beaten by enigmatic veteran Tidal Bay in a barnstorming finish to the Lexus Chase.
The feature event of Leopardstown's Christmas meeting and the most-anticipated race of the festive period on both sides of the Irish Sea, the Grade One contest looked a mouth-watering race on paper and lived up to the billing and then some.
Flemenstar was a hot favourite following his devastating performance in the John Durkan Memorial Punchestown Chase earlier this month, although the question remained over whether his stamina would last out over three miles.
The Willie Mullins-trained Sir Des Champs had been well beaten by Flemenstar at Punchestown, but the extra distance was expected to bring the pair closer together.
Flemenstar jumped and travelled with his trademark panache, albeit with more restraint from Andrew Lynch in the early stages, and as he moved stylishly to the lead rounding the home turn, the crowd were sensing the imminent crowning of a new champion.
However, it was clear on the approach to the final fence Peter Casey's pride and joy was beginning to tread water and from there the drama ensued.
Flemenstar jumped the last obstacle in front, but was soon passed by First Lieutenant, who then looked likely to take the honours for Mouse Morris.
But then the complexion of the race changed again as Paul Nicholls' British raider Tidal Bay, who looked cooked leaving the back straight, finished with a rare rattle under an inspired ride from Ruby Walsh to collar them both.
The veteran passed the post a head to the good over First Lieutenant, Flemenstar was a further half a length away in third and Sir Des Champs was just a short-head further back in fourth.
The latter made a number of jumping errors, appeared outpaced straightening up for home, but came home well to finish right on the heels of the leaders.
The result understandably led to a big shake-up in the ante-post betting for the Gold Cup.
Stan James trimmed Bobs Worth to 11-4 favourite from 4-1, having beaten both Tidal Bay and First Lieutenant in the Hennessy Gold Cup at Newbury, with Flemenstar out to 12-1 from 5-1 and Sir Des Champs is 8-1 from 6-1.
Tidal Bay halved in price for the blue riband to 10-1 from 20-1, but Nicholls is not ruling out switching back to the smaller obstacles for the Ladbrokes World Hurdle.
"He had the right man riding him, you wouldn't want to be in front too soon because you know he would pull himself up, so to have a bit of a scrap and come past them was ideal," said the champion trainer.
"To get him back from where he was to do what he has done today is one of my proudest moments. I believed he'd go well today but you never know. He'd improved from Newbury and even though he's an 11-year-old he's just a high-class horse going forward.
"He's probably the best he's ever been. He'll have an entry for the Gold Cup and probably also have an entry for the World Hurdle.
"What he wouldn't want at Cheltenham is fast ground, but on today's form if the ground was soft he's a big player in the Gold Cup."
