Gotcha??

How do the police get away with flouting the law?  Seems incredible, doesn't it? What's brought this on? Well Humberside police have started using handheld speed cameras concealed in tractors and horseboxes and such on a particular stretch of road where there have been a lot of accidents involving motorcycles..  The Department of Transport say that "vehicles from which mobile speed cameras are deployed should be liveried and clearly identifiable as an enforcement vehicle."  You can argue that what the police are doing is in the interests of road safety, but what about the DoT regulations?  And here's the catch - the police maintain that what the Department put out are merely "guidelines" which they are at liberty to ignore if they wish.  Of course we've been down this line before, more than once in fact - what should be the purpose of enforcement cameras, to catch those breaking the law, or by advertising their presence, prevent them doing so?  Answers on a postcard - to Humberside police.