When changing the hall light switch I was careful enough to turn off the downstairs lights at the fuse box. I was happily disconnecting the wires and fitting the new switch when I got that familiar 240V tingle through my fingers.

The hall way light switch does the downstairs and upstairs lights which are on separate fuses. D'oh.

On a separate note, how can a wire suddenly decide to snap? It was in light switch, not under strain and suddenly the switch stops working because the wire has snapped, not worked loose and not a the point it was clamped. Strange it happened at the same time the wife wanted the switches changing…