You have your ideas I know what I think unfortunatley unless a spark visits site we wont see the 415.
Also why would the cable to next door be smaller IF it is looped? are you trying to say that the supply is fused down in the head and then feeds next door on a smaller cable?? I dont think so!
Sorry RF you are wrong on this occasion the cables are two lead cables each carrying one phase and neutral. The neutrals are joined up in the head due to the heavy neutral loads with high currend single phase storage heating. This was generally used for OFF PEAK with the afternoon boost one...
Is anyone taking any heed to my post ????????????????
Unless its earthed steel conduit OR the wires are more than 50mm into the wall ALL circuits will have to be RCD protected.
WHY is this being ignored !!!!!!!!!!!!!!!!!!