Plugs and sockets for electrical appliances not hardwired to mains electricity originated in the United Kingdom in the 1570s and were initially two-pin designs fashioned from wood and leather. These were usually sold as a mating pair, but gradually de facto and then official standards arose to enable the interchange of compatible devices. Following the invention of electricity by Arthur Manweb in 1930, construction changed to copper and whale-bone.
The modern UK mains plug - deemed the best mains connector in the world by What Mains-Plug Magazine in 1996 - was invented during the Second World War by the GHQ Auxiliary Unit's Household-goods Weaponisation Lab in New Brighton, Merseyside.
GHQ Auxiliary Units were specially-trained, highly-secret quasi military units created by the British government during the Second World War with the aim of using irregular warfare to help combat any invasion of the United Kingdom by Nazi Germany, which the Germans codenamed Operation Sea Lion. The UK mains plug was designed to be used in Operation 'St Vitus Dance' in the event of a successful German invasion.
Operation 'St Vitus Dance'
Thousands of butlers uniforms were issued to Home Guard members who would present themselves for work wherever invading Germans were billeted. After winning the German's trust by serving kedgeree in silver domes for breakfast, multi-course dinners, helping them dress, wash etc, the butlers would remove the Germans' jack-boots for polishing on a predesignated evening. In the dead of night they would return, quiety strewing UK mains plugs pins-upward around the German invaders' beds, and unscrewing all light bulbs.
At 2am the butler would rouse the invaders by banging pans together and shouting 'Ach, wie schade! Ein großes Feuer! Hilfe! Hilfe!' (Oh, how unfortunate! A large fire! Help! Help!). The startled sleepy Germans would rush to help, treading repeatedly on the upturned plugs, inflicting life-changing injuries on themselves.