Why would you ever want to put a switch in an earth conductor? It's an earth terminal. Where would you put the earths if you had complete freedom of choice? And I'm not being arrogant, but perhaps you could explain the contradictions here: You consider yourself a multiply qualified electrical/electronic engineer, and you think that to become competent to do domestic electrical installation work you only need to do some revision and take some exams, as the knowledge is already there. You spent spend a long time learning regs and how household electrics should be done, after which you did some substantial rewiring which all complied with the regulations. You think that earthing conductors can be switched. You don't know how the most common design of lighting circuit found in houses in this country works.