When I did the restoration of my house here, I specified three-pin lighting and the place is littered these sockets, and for a very good reason. I had a traditional pine-beam and bamboo-reed roof (the original roof was long gone) put in to preserve the village nature of the house, so I wanted no wiring anywhere near the inflammable roof - which at 4.5 to 5.5 metres up would be a problem for a fire extinguisher. Thus I had to plan on wall fittings and standard lamps etc. This was another problem. With irregular stone walls the standard rigid electrical conduit would have required on huge thickness of plaster to cover, but if I specified low power lighting wiring I could use a thinner flexible conduit to meet local regulations. The place had to be inspected by the local electricity authority as it had never had power before - or running water, plumbing and sewage disposal, either, come to that! The most surprising thing is that I can still source these fittings over thirty years later.