The Real Whacker was defeated by Paul Townend's mount by two and a quarter lengths, with Stay Away Fay coming in third.
Trainer Mullins will be hoping that 7-2 shot Capodanno's triumph is a harbinger of things to come as he looks to win a fourth Gold Cup at Cheltenham in March.
Townend remarked, "It's a special day, a good prize, and a nice winner."
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