Mullins had great hopes last month that the seven-year-old would deliver the prize he craves so much, but Sir Des Champs was swamped in the closing stages by Bobs Worth.
Davy Russell, who was in the plate here, was prevented from riding the horse then by the British authorities and Tony McCoy stepped in.
Said Russell: “His run at Cheltenham was great, he was only beaten in the last hundred yards and I was disappointed not to be riding there.
“It is important for Gigginstown and me to be winning Grade 1’s. The race only went okay. At one stage, I was just hanging in there and afraid Cheltenham had taken its toll.
“I was struggling to move up, but when we got there he filled up and then quickened. I always knew he was tough physically, but he showed how tough mentally he was today.
“As to next season, if the other fellow (Bobs Worth) stays at that level and we improve a bit, then you never know.”
Long Run — what an admirable horse he is — made a lot of the running and had Quito De La Roque for company for much of the journey.
Sir Des Champs, who seemed to be in trouble early in the final mile, suddenly began to hit top gear and he joined Long Run over the third last.
Russell soon allowed him to stride on, but Long Run, who showed a tendency to jump to his left, was far from finished and rallied in the straight, with First Lieutenant also determined to have a say.
Sir Des Champs just about held the call at last, jumped to his left towards Long Run and then battled on to beat his rival by three parts of a length, with First Lieutenant only another half a length away in third.
A stewards’ inquiry was called, into possible interference at the final fence, but an alteration to the placings was never likely.
For Mullins it was a second success in the Gold Cup, to go with Florida Pearl back in 2002.
Said Mullins: “I thought he was beaten at the stone wall and going to the fourth last. But after that he was a different horse. Davy was very decisive after the third last and was proved right.
“The horse looked big in himself before the race and I was worried. It is fantastic to win, but is not compensation for failing to win at Cheltenham.
“The plan is to go back to Cheltenham next year, I was disappointed he didn’t win this year. I thought he jumped very well there and was disappointed when the ground changed. I’m not going to tell you, but we will change things for the better next year!”
Pat Fahy’s Morning Assembly sprang a 14-1 shock in the Grade 1 Daily Mirror Novice Hurdle, beating the Mullins pair, Inish Island and Ballycasey.
Inish Island did easily best of Mullins’, looking a big threat to the winner going to the final flight.
But Morning Assembly found plenty for Davy Condon driving and went clear on the flat to win with a nice bit in hand at the end.
Said Fahy: “When Inish Island loomed up I thought that was it. But in all his races Morning Assembly has been at his best in the last 300 yards and he kept on at the end today.
“That’s him, he’s a dour horse who stays. He was bought as a chaser and that’s what he will do next season. I have had some good horses, but potentially he could be the best.”
Jane Mangan added to her ever-growing reputation when enjoying a first Grade 1 success on the David Pipe-trained The Liquidator in the Betdaq The Peoples Exchange Champion Bumper.
The winner had been fourth to Briar Hill, forced to miss the race, having pulled out lame in the morning, at Cheltenham and certainly franked that form in no uncertain manner.
Mangan made her move early in the straight and had a willing partner, as The Liquidator eased clear to win comfortably.
Said Pipe: “He’s not over big, but is very tough and gutsy, it probably helped that the favourite came out.
“All he has done is improve and will make a smashing hurdler next season. Jane gave him a fantastic ride, she did exactly what she was asked.”
Dalasiri, who ran badly at Fairyhouse previously, came back to his best when taking the Louis Fitzgerald Hurdle in the hands of Barry Geraghty.
Well-backed English challenger, Richard Lee’s Gassin Gold, looked the likely winner when edging ahead going to the last.
But he spent too much time in the air at the obstacle and Geraghty rallied Dalasiri, who stayed on to score by three parts of a length.
Trainer, Sabrina Harty, reported: “He was held up for a week after his last run, so should improve. He’s a fighter, stays and is very laid-back. You could hack him down O’Connell Street, no bother.”
The layers began their day with a screamer in the Martinstown Opportunity Series Final Handicap Hurdle, victory going to 25-1 shot, Beau Michael.
Sporting cheekpieces and a tongue-tie, he was enterprisingly handled by David Splaine, hitting the front two out and then holding on for dear life to beat Hazariban and The Crafty Butcher.
Davy Condon, successful on Morning Assembly earlier on, completed a double on Klepht in the Guinness Handicap Chase.
Tom Mullins’ charge did well to score, because he ploughed into the second last. He kept finding, however, and seemed to be holding Supreme Doc when that one crashed out at the final fence.
Paul Fahey’s Lots Of Memories battled powerfully up the straight to beat the heavily backed Real Steel in the attheraces.com Bumper.
Mark Fahey, who is a nephew of the trainer, did the steering, and was subsequently suspended for four days for his use off the whip.
* The attendance was 16,410, as against 11,157 a year ago.