I have found a couple of pictures of this gothic creation online, but very few details.
It's said to be based on an Austin FX4 taxi, and its owner (and I presume creator) is called Barry Thompson.
It has "Princess" and "4-litre" badges on the radiator. According to the DVLA website the engine capacity is 3909 cc, so it looks as if it has been fitted with the six-cylinder Rolls-Royce inlet-over-exhaust engine from a Vanden Plas Princess 4-litre R.
I'm afraid that's all I have managed to find.