Yesterday the local primary school had all their electrical equipment
junked. Copiers, computers, everything that was plugged in.
Sockets that were unloaded "sparked and smoked" .All the neons lights
went "very white and bright"

They are on triple phase mains. There were builders in but not doing
anything directly with the electrics.

The first informed comment was that at least 400 volts must have
passed through the place. Nothing can be found as a cause, it just
happened

Everybody denies liability including the suppliers. )

Anybody come across this sort of thing before?