Sneaky Man with Hairdryer needs a Wallop

[andoverben]

I was driving between Andover and Salisbury today on the A343 around 11:00, on coming up to the Army base near Wallop I was greeted by several cars flashing their lights and waving at me out of the window. [ I have now cottoned on to the fact that in all likelyhood they are warning me that there is probably a Hairdryer touting Man in a Van up ahead and my 'press on' style of driving might attract unwanted attention. As opposed to hey there young whippersnapper you are driving far too fast on this clear dry bit of road and should proceed at 40mph like we are in a NSL which would of course be greeted with a salute of the 2 fingered variety. (I would just like to appologise to the man in a Mondeo about 4 weeks ago on the A303 who warned of a Hairdresser and I took his warning the wrong way!)] I slowed down to see a Police car in a Layby with another Panda Fiesta Parked further down the road Mounted up on the pavement so it could be hidden behind a large potted plant!!!! cue him out of the car holding what looks like a gun hidden behind his back!!

I warned anyone coming the opposite way of this gratutious use of the vegitation. Surely if they are supposed to be a deterent then the idea is you can see them? How would one stand if you were caught by him, would it be possible to argue that he was not visible? am I right in thinking they are supposed to be so for any ticket to stand?