It was a close thing for second, with Cue Card just holding the late rally of Silviniaco Conti.
Scudamore said: "For the first time in my life I'm pretty speechless. It's wonderful - I thought he'd win, but I never imagined he'd do it as easy as that.
"He's a phenomenal racehorse, he's a pleasure to ride and a great credit to everyone. To win a King George on his fourth run over fences, it just shows the hard work everyone back at the yard has done and I'm so thrilled to be part of it."
He added: "Between myself, my father (Peter) and grandfather (Michael) we've had about 33,000 winners and he's the best one of the lot."