I was slightly involved in installing ANPR cameras on both vehicles and motorway gantrys several years ago.
They are all over the place now, including supermarket carparks and petrol stations. Most are automatically relaying all info back the DVLA who can then issue alerts or fines automatically. There are also DVLA vehicles with corner-mounted ANPR cameras that cruise about clamping vehicles as they go.
Any plod on the beat could call in for a PNC2 check on a vehicle, and most vehicles had access too, so years later it's probably even more advanced. And don't forget that the ANPR system is connected not just to the Road Tax database, but to the MOT Test and insurance databases too. Very Big Brother but, AFAIC, very worthwhile.