There is a date if you can search for it, on which the UK use of "trade plates" by commercial organizations was tightened up considerably. A number of bigger country estates, mining companies and garages had vehicles which seldom appeared on the public highway. These could be kept exempt from road tax .But when they did need to travel on the road system it was common for the estate to have trade plates for the short trip it might make. A vehicle originally issued by Government to be used by consular staff on some commonwealth Island territories might have no UK number until it returned . Some Islands did have a registration system, but the number applied to any vehicle was issued annually. Or as in Switzerland the plate number for any vehicle is issued to the owner not specifically to the vehicle. Any number of reasons a Land-Rover might never have been registered here.
