In the relatively near future we will look back with fondness at the RAF Police. *we* are moving towards a tri-service, nondenominational police force. Would you rather deal with a relatively sensible RAF Copper, whio has been taught RAF ethos etc, than a redcap who can only just manage to walk and talk in the same week.
As to tax discs etc, *most* criminal activity is carried out in vehicles untaxed or insured, its just one indicator.
and I am not a copper!