Close, Frank. It was a man by the name of John Dodds. He was an independant Rolls-Royce gearbox specialist. The car known as "The Beast" was built based on a Ford Capri, using a lot of fibreglass by a man called Roy Phelps, the founder of Santa Pod raceway and like you said, had a Rolls-Royce grille on the front. The engine used was a Rolls-Royce Meteor, the same as a Merlin but without the superchargers, but still made ~1,500bhp and destroyed gearboxes easily.
My grandad, who used to own a Rolls-Royce dealership in Essex knew him.
It later caught fire, and was rebuilt using a Schimitar body, it's still around today, owned by Dodds' son.
The Beast: