thank you johnny_t
Well, I only disconnected the parallel branch within the mirror light that goes to the transformer (that was the intention at least). And also, there are only two wires feeding the mirror light from the wall, live and neutral (red/black). Is it still possible that the last...
Here is my case:
Step 1: Isolated yesterday 2nd floor lighting from main switchboard to remove from mirror light the shaver socket transformer which blew 2 Saturdays ago (2nd floor lighting switchboard switch did trip at the time).
2nd floor lights comprise: 1. main bedroom group A spot...