The Gorse Fox related, last week, the problems he had encountered on his home network and how, at some expense, he had managed to almost cure them. (Indeed he thought he had cured them).
It became clear that there was still a gremlin lurking in the network. There seemed to be two entirely separate address ranges in play. A little bit of research suggested that the addresses chosen could be the result of DHCP not being available.
Knowing that the DHCP server was available, the Gorse Fox worked back through the network and discovered the miscreant. He has a Powerline network. Segments of the network are connected over the house's power grid - rather than running cables round the walls. The very first link from the Router/ADSL modem to the power grid had failed. There three lights than indicate some lifeforce had flat-lined. The plug was dead, deceased, it was no more. Had it not been in the wall it would have been pushing up daisies.
A 20 minute trip to Chi afforded a simple replacement. Et voila, everything is now hunk dory. (The Gorse Fox should have spotted this last week!)