So, big Victorian house, rewired in '95 or '96. Looking round it seems a tidy installation, then I go down into the cellar. Never mind your spring clamps and such like, or contacting the DNO. This is how you sort a DNO earth connection. Separate the wires and twist them round the lead sheath, then apply solder (silver mind) pigeon style. Get so much heat into it you burn the erth cable sheathing, and finally tape over to prevent too much of your soldering being on show as opposed to offering any insulation or protection.