Horsefeathers -- was it a DDOS or a failed upgrade?
To air is human but to really fuck things up is a oft overused phrase.
You don't take down a couple hundred thousand users without either being hit by a DDOS or an upgrade gone wrong. No one could be so cheap as to have a SPOF or could they?
Perhaps, BT couldn't get through to the scummy helpLESS lines in OpenReach to get help? That'd be fitting karma!