In doing some plumbing around electrics I accidentally dropped the hammer and smashed the casing on an old black junction box. I have replaced but realised there was an additional
single black wire (see image) which doesnt seem to have a purpose it goes through the wall into a bedroom junction box and ends. I have tested it is not live. Is it an old continuity live? I assume part of the original wiring which is early 60s. Is it still required?