Other situations that are indicative of a well-resourced group carrying out surveillance:

The registration number of a car or vehicle shows the location of where the vehicle was originally registered. With the more modern type of the form WA17 CVA, say, the first two letters indicate this, and for instance, WA through to WL indicate a car registered at Exeter or Truro. Thus such numbers appear more than others in this area. Northern Ireland registrations are of the form GMZ 7182, for instance, and of course wouldn't be highly represented in the Plymouth area.

I will be suggesting that sometimes there are a lot more than can be expected by chance, and that this is due to a surveillance department in one area sharing vehicles with that of a police force in another.

The following video shows a car with NI registration, where there is some suspicion that it is following from the front, as it were...