Just a point

In the UK Vehicle Licensing (i.e. road tax) is paid on every vehicle. It is illegal to drive a vehicle that has no tax paid on it. Fuel duty is paid on petrol, diesel and anything else the Treasury decides to tax, and is payable when the fuel is bought.

If the guy was done for not having "road tax" then it would have been nothing to do with the fuel that the vehicle was using. However, if he was manufacturing a fuel that had duty levied on it then he would have been done for evading duty - much the same as if a person tries to smuggle in alcohol or cigarrettes.

Pete

God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!