9:03pm, Tuesday 1 July 2003 (Updated 10:49am, Wednesday 2 July 2003)
The following day, I noticed another on a rusty old signpost a little way down the road. What are these boxes for? The label, "DANGER High voltage", doesn't give anything away. I'd be surprised if an old signpost pole had a high voltage electricity supply, but the back of the box does appear to have a sealed gland connecting it to the post so I guess it's possible.
Any clues, please let me know.
According to the helpful folks in cam.misc (thanks!) these boxes are probably radar or microwave speed or proximity detectors. It looks like the council is conducting a survey of vehicle speed.