Thankfully the PC's seem to be ok but definatelly food for thought, everything was on surge protection plugs can only wonder if the cable moden took a direct hit from the coax cable that runs up the side of my building straight into the VM modem and took the switch next to it?
If that was an incoming path, then what was the outgoing path? No outgoing path means no damage. A surge does not enter, do damage and stop. First that current is everywhere in a path through the sky, through the modem, and maybe kilometers to distant earthborne charges. Much later, something in that path fails - ie the modem.
Irrelevant if wires were overhead or underground. Risk remains same. If cable was properly installed, then it had best protection. A wire from the cable to earth. No protector required. And therefore not an incoming path.
So what happens if a surge is incoming on underground AC power? All but maybe one wire have no connection to earth. A direct strike far down the street is incoming to every household electronics. But a hunt for earth only found a path via the modem.
Damage is often on the outgoing path. That would be via a modem to the properly earthed cable. Nothing inside will avert that hunt. Once permitted inside, that transient current will hunt for and damage a best connection to earth.
Adjacent protectors did little if anything. Better protection was already inside every appliance. Modem, as the best path to earth, actually was doing protection. Once it because a best path from cloud to distant earthborne charges, then nothing inside the flat will avert that current flow.
To have damage means an incoming and a completely different outgoing path existed. Damage on the cable side of that modem means that may have been the outgoing path. Since lightning is rare in the UK, consumers typically should not see damage. But the UK also has virtually no surge protection - which is what adjacent power strips essentially are. They do not even claim to protect from this type of transient. And in some cases can make damage easier.
