[emeritus]

At Plessey Ilford they once had a poster campaign, advising engineers not to wire up plugs themselves, but to get the electricians do things properly. We had recently had them install some additional 13A sockets in our workbenches in readyness for a new project. The bench had wooden trunking (essentially a plank screwed at 45° in the corner between the rear of the work surface and the vertical back board). When I plugged a second soldering iron (resting on the same heat sink as the first), into one of the new sockets, there was a flash and the bench's circuit breaker tripped. Resetting and testing with an Avo established crossed L and E, and unscrewing the offending socket (after isolating the bench supply at the wall) revealed that the bench wiring was in solid conduit wire. They had evidently run out of green wire, and all the new sockets had red wire for both L and E. The electrician had not bothered to sleeve the "earth" Red, and had got the two reds transposed half way along. As the sockets were screwed into wood, and the fixing screws passed through eyelets connected to earthed metal strips at the back of the sockets (plastic), the screw heads used to secure the incorrectly-wired sockets were also live.