Never really got to the bottom of it. At the time i was fitting it out and wasn't permanently plugged in (only when I was using 230v tools etc on extension leads). I suspect it was a nearby, fairly new, Colecraft with liveaboards. The strangest thing was that on one side about 6" above the baseplate there was a perfect 'pit' in the form of a cross exactly as one would imagine a fabricator marking a spot with a sharp instrument such a file or screwdriver. The hull had been blacked from new by the builder. I sat on a low stool with a welder, a grinder with a wire wheel and another grinder with a grinding wheel for two days. Quite enjoyed myself.😇