On Feb 15, 11:31 am, EricP wrote:
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

230 volt electronic appliances are expected to withstand spikes of
up 1000 volts without damage. If the spike were longer, then that
maximum number would be lower and the event would be more obvious in
lighting.

A ballpark idea of how large a spike would be to do so much damage.