The neighbours in the communal garage compound saw me filling up with 20 ltr barrels of YELLOW fuel. HMRC arrived one NIGHT (9pm) with 2 vans and a class 2 LCV with a portable lab on board and announced that if they found the smallest chemical trace (all fuel sold in Europe has chemical markers) of none road fuel in the tanks of my 4x4 and £30k motorhome they would be seizing both on the spot. They handed me a booklet with their powers which they might as well not have bothered with, as with "reasonable suspicion" they can enter ANY non dwelling if need be by force to seek evidence and they told me they could get a warrant for the house in under an hour!
It scared me witless, however luckily I had registered a a fuel producer about 18 months earlier and even paid tax on the biodiesel I had produced, so when there lab failed to identify any illicit fuel they stormed off saying that they would hear from me with a result within 12 weeks...I never heard from them again.
It was all perfectly legal but I was banned on the spot by SWMBO from using BD ever again. It really was not a nice experience, so what would I do?...I'd get my walking boots on!