My dad drilled into a wall with an unmarked 3 phase cable behind it, took out the fuse at the substation. 🙂
Mind you, I once pushed a wrong button on the lighting desk at a theatre with a somewhat, uh, “rickety” set of dimmer racks and accidentally turned on about 50kW of stage lighting in a snap fade. Saw the blue flashes from the electrical bay through the varnished wooden floor(!), then the power went off. Then the burglar alarm went off. Went outside looking as nonchalant as possible and discovered that power was off to most of the town…
After that incident they replaced it with a proper 3-phase installation. 🙂