Do you also have an RCD[1] in the mains switchboard? Each circuit breaker in my shiny new upgraded mains switchboard is also an RCD.

I still occasionally see an old switchboard with ceramic wire fuses with the fuse wire replaced with a bit of coat hanger wire, or the correct fuse wire wrapped around the terminals ten times. They often seem to be the same houses that give you a tingle if you touch any of the metal plumbing fixtures. Yikes.

1. https://en.wikipedia.org/wiki/Residual-current_device