Nicholls, owner John Hales and jockey Ruby Walsh have suffered heartache in this race before with the ill-fated Granit Jack, but the 8-1 chance went a long way to exorcising those demons.
Still under a tight hold at the top of the hill, where, first, Hunt Ball and shortly afterwards Grands Crus had run their races, Walsh was joined by another grey, Walkon, and held just a slight advantage two out.
He stamped his class on proceedings from there, defying a huge weight burden to hold off the late challenge of the Alan King runner up the gruelling hill to finish three lengths clear.
Nadiya de la Vega was third with long-time leader Casey Top running a gallant race in fourth.
Nicholls said: "He came in late because he cut himself in the field, but he had a gallop at Wincanton last weekend and went really well.
"Everyone thinks we want to win the trainers' championship, but it's not true. Days like this and bringing young horses through are what makes it all worth it."
Hales, owner of the great One Man, said: "That was as good a performance from any horse I have owned. I think we have decided we will go to the King George now."
Walsh said: "You need a bit of class in this race, which is why we were keen to take a chance. In fairness to him we were forcing him at two miles. Stepping up in trip is probably what we should be doing."