i may be wrong, but looking at the 4 pic i would say that isnt a cable but conduit possible coming from main fuse internal, contact dno , DONT interfere with it, i know what happens when things go wrong, i have 24 years exp with sweb/wpd, the dno will have to replace cutout , renew cable if not capable of 15kva at no cost, you're not allowed to isolate at the cutout unless authorised by the dno. --------, you may be able to get an earth from them too