What A Friend was well beaten by Cooldine at the Cheltenham Festival
What A Friend, part-owned by Manchester United boss Sir Alex Ferguson, won the Lexus Chase at Leopardstown.
The 11-2 chance, runner-up to Denman in the Hennessy Gold Cup in November, stayed on to beat Money Trix and Joncol while favourite Cooldine disappointed.
What A Friend, trained by Ferguson's friend Paul Nicholls, was ridden by Denman's former jockey Sam Thomas.
Meanwhile, Solwhit won the December Festival Hurdle to enhance his claims for the Champion Hurdle in March.
Bookmakers reacted to What A Friend's victory by cutting the six-year-old to 20-1 from 33s for the 2010 Cheltenham Gold Cup.
The three-mile chase, which traditionally features some leading Gold Cup contenders, was rearranged after fog caused Monday's card to be postponed.
Thomas, who was on board What A Friend in the Hennessy, only got the Lexus ride after Barry Geraghty was rerouted to Newbury.
"If you take Denman out he would have been a good winner of the Hennessy and all credit to him for coming here three weeks after that run," said Thomas, who won the 2008 Gold Cup on Denman but has endured mixed fortunes since.
"People thought he was ungenuine in the Hennessy when he wandered about going to the final fence but he was just trying so hard.
"Some great horses like Denman and Beef Or Salmon have won this race so hopefully our horse can go onto bigger and better things and I think he might come back here for the Irish Hennessy."
Cooldine, who won the RSA Chase at the Cheltenham Festival by 16 lengths in March when What A Friend was last of six finishers, was sent off the 100-30 favourite.
But trainer Willie Mullins had warned he might need the race and he faded in the closing stages under Paul Townend, who stepped in after Ruby Walsh chose to ride Big Buck's for Nicholls in the Long Walk Hurdle at Newbury.
What A Friend, who had a 22lb weight advantage when second to Denman in the Hennessy, travelled well throughout.
He stayed on for an English 1-2, gamely holding off the Nicky Richards-trained Money Trix (14-1) by half a length with Joncol (7-2) in third.
Joncol's trainer Paul Nolan said : "It is unfortunate that we seem so far behind the English horses.
"For What A Friend to come over and beat us like that, it puts us a long way behind.
"Hopefully he will improve a bit with age and I am delighted with his run, but I thought that we did have it."
It was the biggest National Hunt win so far for Ferguson, who jointly owns the winner with Ged Mason.
The Manchester United manager has enjoyed mixed fortunes during his forays into racehorse ownership.
Ferguson led in the brilliant Flat horse Rock of Gibraltar during his early successes, but an ownership dispute saw him come off second best in a row with wealthy Irish racing duo JP McManus and John Magnier.
In the big hurdle race, Davy Russell pushed out 8-11 favourite Solwhit to win for trainer Charles Byrnes.
The 2007 Champion Hurdle winner Sublimity (5-1) was two lengths behind in second.
Lexus Chase 3m, Leopardstown
1 What A Friend (Paul Nicholls) Sam Thomas 11-2
2 Money Trix 14-1
Dist: 7-2 ½, 1¼. 11 ran
Leopardstown Golf Centre December Festival Hurdle 2m
1 Solwhit (Charles Byrnes) Davy Russell 8-11f
2 Sublimity 5-1
Dist: 2, 2½. 6 ran