When we recently covered the topic of high voltage safety with respect to mains powered equipment, we attracted a huge number of your comments but left out a key piece of the puzzle. We take our mains plugs and sockets for granted as part of the everyday background of our lives, but have we ever considered them in detail? Their various features, and their astonishing and sometimes baffling diversity across the world. When you announce that you are going to talk in detail about global mains connectors, it is difficult not to have an air of Sheldon Cooper’s Fun With Flags about you. But jokes and the lack of a co-starring Mayim Bialik aside, there is a tale to be told about their history and diversity, and there are also lessons to be taken on board about their safety. In the earliest days of domestic electricity, by far its most common use was in lighting. Just as they are today, lighting circuits were hard-wired to receptacles designed for incandescent bulbs. When the first portable domestic appliances appeared they thus only had access to power through lighting sockets, and some of the earliest mains plugs simply replicated the base of an incandescent bulb. As appliances prolif...