At my former work, we had a non-rcd incident many years ago...
An offshore cabin was in the yard, for maintenance.
It was hooked up to a 3-phase electrical supply with a Commando-type plug, from a 64A supply.
It only used 2 of the phases, to feed a single-phase transformer.
This was working fine.
The person who wired up the plug had wired the 3rd phase to the earth pin.
The entire cabin was floating at 240v above ground potential, on a 64A breaker.
This went un-noticed until someone had at it with an earthed drill.
As soon as the bit got through the paint, there was an almighty BANG.