I've worked with several retired Customs and Excise officers. Their comment was, with three hundred years of history we have some very robust powers, and had some very, very funny stories.
I doubt it but they are quite likely to do a random check and issue a warning, they usually only act on information or visit sites where there is a possibility of detecting someone. Many years ago it was common to see them at Game Fairs and the like so a private punter is highly unlikely to get checked.
Yes - I'm not suggesting trying it, more interested in the possibility of accidental contamination.
Back in the day when I worked for ICI, that is giving my age away, our long distance lorry drivers usually departed with 20,000 cigarettes on the waggon; to 'smooth' border crossings past West Germany.
There is a video around of the police pulling over a electric van to do a diesel fuel test on it. Needless to say they struggled to find the fuel filler cap.
Get the ferry across to Dartmouth and fill up .
There is no taxis I kings wear.
The police have no interest in the fuel, or lack of it, in a vehicle. Customs yes, police no.
It was one of those police camera action type programes where they were checking vehicles at random. Some police had basic colour test kit and would request hmrc attend if red was found.
The "A big boy did it and ran away" defence seldom seems to carry much weight with Authority.
That smacks of lingering bitterness!