In Wiltshire the Police are more concerned that the plates can be read by cameras than strict legal compliance.
So if you have a 3 letter/3 number plate on a Mog it is unlikely they will care, but if you have a more recent plate in Black and silver they will.
Which leads me to ask, is the rear number plate on my 4/4 legal? It is a 1982 model and has the aluminium bumpers fitted. The rear bumper overhangs the number plate bracket by quite a distance which obliterates any clear view of the plate unless viewed from distance. I have noted that unmodified Morgans of the same era with bumpers fitted have the same indistinct rear plate. So it left the factory like this, but does it mean that it passes the present day legal requirements