We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Steve Walker
saying something like:

Nope. Any car parks, roads, etc. that the public have access to can now be
considered part of the highway for road traffic enforcement purposes.
Anyone sensibly using an empty car park for a bit of skid pan practice can
be done for dangerous driving or any other such offence. People have also
been done for not being insured when having a go of other peoples vehicles
in car parks or for not stopping at a pedestrian crossing in one.

As well as that, if someone sees you doing it and reports you to the
police, you can be warned and then, if on a second occasion, a separate
person sees you doing it (or something else) and reports you, you can be
summararily convicted of using a vehicle for anti-social behavior and can
have your vehicle confiscated for a couple of weeks (of course, you will
have to pay for it being towed and stored before you can get it back!)

It's always been the case though, that some coppers are utter ******s.