The installers had wired the boat using 2.5mm twin and earth solid-core cable throughout. In the forward hold, the cable had been loosely draped across the void and left unsupported.
The customer proceeded to use the area as an attic, filling it with assorted objects, some heavy- and in time the cable became caught and was supporting a bulky object.
As the circuit was a ring main, and the power source a large genset, the cable became warm in use- and under the influence of weight, began to stretch. Copper is ductile, and instead of breaking, it became thinner and thinner- and resultantly hotter and hotter.
The customer was in blissful ignorance of the resulting fire, which fortunately burned itself out after consuming the polystyrene next to the cable. My brief was to investigate constant tripping of the boat RCD.