It had a 28-litre Spitfire Merlin (or "Meteor" without supercharger) engine with a bespoke automatic transmission. This is probably around 1,500bhp.
"In the 1960s John Dodd of Kent, England put a Merlin engine (some say it actually was a Rover Meteor tank engine, but then this is a Merlin minus superchargers) in a car called "The Beast". Originally it had a grille from a Rolls Royce, but after complaints from them he had to change it. According to himself he once drove by a Porsche driver on the autobahn and this person then called Rolls Royce asking about their "new model". The Beast was once listed in the Guinness Book of Records as the world's most powerful road car. The engine came from a Boulton Paul Balliol training aircraft and gave 1262 bhp (941 kW) at 8500 feet (2,600 m). In the car the supercharger was removed so it "only" gave about 850 bhp (630 kW). The chassis was custom made with a fibreglass body and used a gearbox from a GM 400. The car was later restored by John Dodd's son Paul Dodd and he also has a 2050 bhp (1530 kW) twin-supercharged Rolls-Royce Griffon 37 litre engine from a late-model Spitfire he is willing to put in a car if somebody would be interested in buying it."
My mate Tony Lauder used to live opposite John Dodds house in Links Road, Epsom during the 70's. I saw the car often, as it wouldn't fit in the garage. The back end used to stick out from under the door.
Whenever he fired it up we would go out into the road and watch, sometimes he was just moving it, other times he went off in a cloud of smoke. It would do 70mph in reverse.
He was an independent Rolls Royce gearbox specialist (That's what was on the side of his van anyway). The original body was Ford Capri, and was really rough inside, the re-incarnation (after the fire) I think was from a Scimitar, also glass fibre.
The pics above were taken at Santa Pod, I was there and couldn't believe the distortion of the chassis as he gave it full power - great sound though.