Sizing John has given trainer Jessica Harrington her first victory in the Cheltenham Gold Cup with her first runner, coming home a clear-cut winner of jumping's blue riband.

So often in the shadow of the mighty Douvan over two miles (3200m), the seven-year-old completed the English-Irish Gold Cup double in style to dispel any stamina doubts.

Given a patient ride by Robbie Power, Sizing John kept on strongly up the hill to score by 2-3/4 lengths from Minella Rocco.

"I can't believe it. It was amazing how he jumped and travelled," Harrington said.

"I've never had a runner in the race before so to train the winner - I don't know when I'll come down to earth.

"You can tell Robert did showjumping in his youth because I don't think he missed a beat the whole way.

"I was thinking it was all going a bit too easy. I was glad that on the first circuit he put a few short ones in and he wasn't winging fences.

"When he pulled him out on the second circuit, he began jumping well. Just at the top of the hill I saw Robert give him a squeeze and he flew.

"He's only seven so I've got to keep him right and mind him. I've no idea what he'll do next, all I was thinking about was this race."