In an Edinburgh flat, the lighting circuit wire is still partly
vulcanised indiarubber in steel conduit. This isnt going to
last forever, but the conduit runs up from the light switch
behind an ornate cornice that we dont want to damage. Is it
permissible just to replace the singles with modern PVC
insulated ones? My concern would be that PVC is subject to
creep, and I dont know the condition of the corner where the
conduit turns from the wall across the ceiling. Is there some
way of working around that? It may be possible to access the
corner from above, but that involves cooperation from the flat
above, so it would be useful to be able to plan options in
advance.

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Jón Fairbairn
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2014-04-05)