Holywell broke a run of four second places this season with a hard-fought win as Jonjo O'Neill saddled first and fourth in the Pertemps Final.
Ridden by Richie McLernon, the 25/1 chance travelled smoothly into contention in first-time blinkers and although horse and jockey both needed to work hard after the final flight, the winner found plenty for pressure and gamely held off the challenge of Captain Sunshine (11/1) by a length and a half.
Jetson made late gains from off the pace to finish third, while Tony McCoy was left still waiting for his first winner as he finished fourth on the better-backed stablemate Shutthefrontdoor (6/1).
"The blinkers obviously helped him - Richie said to put the blinkers on him after he ran at Haydock," said Jonjo O'Neill, saddling his 22nd winner at the Festival as a trainer.
"Shutthefrontdoor was a bit novicey and a bit big and bold, whereas the other fella is a bit cuter.
"Everything went right for him. He jumped great, he had a great run around - it just went right.
"It's fantastic. Trainer or jockey or whatever, everyone dreams of getting into that winner's enclosure at Cheltenham."