It might be of interest to know that I saw a mobile speed camera van on the A168 (southbound) at the weekend. We passed it when travelling northbound. This is a road that has no speed camera warning signs at all - I made a point of checking when we returned down the same road later on. Apparently although DfT rules say that there must be warning signs where speed cameras are in use, not having any signs does not let you avoid prosecution. So that's fair too?
Be warned.
Be warned.