Houses built in the 60's often only had one RFC to supply all the sockets in the house, having said that it was only one double in every room. The kitchen might have got a few more.
Thats what I was trying to say, also you could be a member that has hit the "target", for one reason or other not been on for ages and still retain your "badge".
I remember back in the 80s with pme earthing arrangements some electricians were running 16mm earth for absolutely everything even cross bonding. Most 60A supplies the main earthing conductor was 6mm
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