Fair enough.I'm told it was the Home Office John, the hows and whys escape me, however the words "crown immunity" often also come up: .... So defintaly pre RCD era ... Thats all I know John, like I said, I imagine it probably was relativly rare.
The main part of this which I really don't understand is that, to the best of my knowledge, there is no (and never has been any) legislation or other mandatory regulations which could explicitly 'prohibit' this practice, so it is not very clear who could, or would need to, "give special permission' for it to be done.
BS7671 and, I presume, the Wiring Regs before it, certainly does 'prohibit' the practice, but there has (to the best of my knowledge) never been any obligation to conform/comply with those. Even today, the guidance (Approved Doc P) to the legislation (Part P) merely indicates that demonstration of compliance with BS7671 is one way of demonstrating compliance with the law - and, in any event, we are clearly talking about a time (pre-RCD era) long before Part P.
If it were done today, in violation of BS7671, one would certainly have to be able to produce a "special argument" that it was compliant with the law (Part P), but that would be down to the perpetrator, and I am not aware of any person, government department or body who would/could be able to "give special permission" which meant that the perpetrator did not have to produce his/her own argument.
I'm not doubting what you're saying of the past - I merely don't understand exactly what it meant! I suspect that the truth may be that it is something which was simply sometimes done (without any "special permission from anyone), contrary to what the Wiring Regs of the time said, but that there was no compulsion to comply with those regs.
Kind Regards, John