Does anyone have any brilliant ideas about how to ensure the main
power switch remains off when someone is working on the wiring?
The switch is inside a metal box that is locked with a padlock.
When the wiring is being worked on, a warning sign saying "LEAVE OFF"
is locked into the padlock, together with the name of the electrician
and his mobile phone number.
Dozens of people have keys to this padlock, as they need to switch the
power on each morning and off each night.
Unfortunately some are not very observant and don't notice the warning
sign. The electrician was rather lucky to notice when the power came
on again.
I suppose that temporarily changing the padlock would be a start.
However some people are known to use bolt cutters on padlocks when
they feel they are entitled to open them.

Perhaps another metal box with a flush lock could be placed over the
existing box.

Any other ideas? It's too late to sack a moron after the electrician
is dead.