Pictures and info submitted by SanUK:
Heres a few pics for the photos for discussion forum i took today on a job yesterday, to move a consumer unit onto another wall ( about 1 meter away).
Was under the floor sussing out cables as nothing was marked, and found this J, thought it was long dead.
But my trusty VOL-CON elite told me otherwise. And it never even blew the fuse (rewirable). Little info. 2.5mm T+E leg from a ring main returning to the CU, jointed in a 30A JB. The phase conductor was melted all the way back to the white clip in the pic.
Water must have filled the box as its below the kitchen.
Heres the pics: