When selecting csa of main bond for PME system, I look to the DNO neutral at the point of connection of their supply. I have a 185 Waveform providing a supply to a 100A TPN whole current meter with the tails at 35mm2. So big end box but relatively small installation. I have specified 50mm earthing conductor and MPB to comply with 542.3.1 and 544.1.1. Just having a moment of doubt (you might know how that feels as one creeps past 65!)
