Years ago a mate of mine stuck press studs on both his front and rear number plates and when the coppers stopped him he said sorry I forgot to put them back on, they been stolen 4 times and you boys aint caught the guy doing it yet, so now they are detachable!! (he did have his plates stolen several times while he was at his GF's house overnight as she lives in a pretty shonky area), he always kept the plates in his boot and just stuck em straight back on when he got stopped.
I think he used to get stopped about twice per month, on the plus side I believe he had fun driving back and forth through a speed camera at night one fine evening, he said they must ahve had about 50 pictures that night of a black car with no plates