Hi folks,
Thanks to those who responded to my earlier about possibly non-copper wire in my ring main.
Now I've managed to hawl some out, I can see that it is indeed copper inside after all, possibly coated with tin. As one poster suggested, there are 7 strands.
The rewiring of these particular rooms by a past owner must have been at a time when this kind of wire was used. My recent work hasn't replaced all of it, but as part of adding sockets to my wife's study I now have one less room with the stuff.
This is a good thing - it's surprisingly hard to wire a socket with all those strands jumping about.
regards,
Ewan