Grand Partner and David Mullins © Photo Healy Racing
Grand Partner swooped on the outer to spring a 25/1 shock in the concluding bumper at Fairyhouse.
There were plenty in with chances turning for home in the two-mile contest and On Impulse held a narrow advantage going to the final furlong as Lord Scoundrel and Most Peculiar pressed.
The trio were trumped in the closing stages, however, as David Mullins got a good tune from Grand Partner to land the spoils.
The Millenary gelding, trained by the rider's father Tom and owned by his mother Helen, went on to record a length-and-a-half success over 7/4 favourite Lord Scoundrel.
The winner had been a well beaten fourth in a maiden hurdle at Thurles on his last outing just over a year ago.
“He had the experience of a couple of runs over hurdles. We gave him a break and he strengthened up. He's improved mentally more than anything,” said Mullins senior.
“He's a cheap horse, I bought him for €1,600. I thought David gave him a good ride.”
(Additional reporting by Alan Magee)