There are quite a few references and photos of The Beast in my book (please excuse the plug www:streetrodandcustomshowtime.net) and John's Merlin actually uses some parts from the tank engine. The bodies have all been built by FGR in Shortlands (FGR are also the people who started Santa Pod Raceway 50 years ago) and the first was damaged in a fire in Sweden and the second, which is very similar to the current body carried the RR grille. John still has it and came to the Malaga Motor Museum event in it last summer. It uses Austin Westminster front suspension and a MK10 Jaguar back axle.
Never the prettiest of vehicles but it did bring a fantastic amount of media interest to an embryonic custom scene back in 1972 when it was first shown. Why? John was an automatic gearbox builder and created a box for it. What better way of advertising your business than building a gearbox that could handle 850 bhp in 1972 remember - a time when most production cars had less than 100 bhp available.
Most of the Merlin engines that were built in the UK were built by Ford, under contract, at their Manchester plant.
Cheers