Frodon became only the second four-year-old to win the Caspian Caviar Gold Cup when outpointing older rivals in the valuable handicap chase at Cheltenham.
Trainer Paul Nicholls sent out Unioniste at that tender age to score in 2012 and repeated the trick with Frodon (14-1), who was providing Sam Twiston-Davies with a big-race success after returning from injury.
Last year's winner Village Vic made a brave attempt to make all the running and stuck to his task for minor honours when the pace warmed up.
Kylemore Lough took the lead before the second-last but Frodon, who had run better than his place suggested in the BetVictor Gold Cup last month, ranged up menacingly.
Twiston-Davies drove him right out to land the spoils by a length and a half from Aso. Village Vic was a head away third and Quite By Chance fourth.
Twiston-Davies said: "I said he had a good chance, and it's important for me coming back from injury to get a big one on the board for the boss - I couldn't be happier.
"If he hadn't made a mistake at the ditch down the back the last time, you wonder what might have been.
"I was happy with my position and that's what we wanted to do today, give him a bit of space and the right horses to aim at.
"He jumped the last really nicely, but when the ground is like this, it's a long old run-in."
He added: "These days are very important. He's brave and it's a very special day."
Nicholls said: "I enjoyed that, I thought he was awfully unlucky the last day. The rain suited him and I thought he'd go close today."