blackwolf wrote:

Perhaps they're false plates?

Balvaig wrote:

Possibly a Government owned car? I used to drive one - no tax, insurance or details on record. Great fun if you were stopped for any reason.

TexasRover wrote:

Obviously anyone could put any plate on any car, you can probably have plates made up, just plastics, or swap between vehicles. Illegal obviously but if you were to pass one of the number plate recognition cameras, or a police car with one, there will be lookup in the database, including I imagine the more secretive ones, to check if the car is legal to drive on the road. Just because we cannot find a record, does not mean the 'government computer' can't check if its ok.

I doubt they compare by computer the car (type, colour) etc on the picture so if you were to swap between two legally registered cars (tax, insurance and MOT) it would probably not trigger anything..

Until you get stopped and they check the details or are involved in an incident.

You wonder what happens if you just invent a random number that does truly not exist, I suppose the stationary camera just logs, but there is nothing that can be done, but I expect a patrol police car with a reader would make it flash up red on the screen and they would go and intercept.