I remember this guy who was nicked for speeding on the M1 shortly after it was opened. It was said that he was still in second gear at the time!
He shoehorned a RR Meteor 27 litre Centurion tank engine into a chassis and had the body made to fit around it. Also had trouble with RR because the car had a Rolls Royce radiator fitted and they wanted it removed.
This engine was virtually the same as fitted in a Spitfire and other types, except it didn't have a supercharger fitted. That said, it was more than enough power for the owner! TC.