It was the style plates that were the issue, some years ago, they seem to have died out.
In extreme circumstances if your plate does not meet legal specs, i.e. Spacing, style, coloured screw caps altering numbers or letters, or mini plates, you can be reported to DVLA and your plate replaced by a "Q" plate.
I've known a few cocky motorists, with appalling style plates, receive letters from DVLA. They thought the likelihood of their precious costly plates being confiscated was untrue.