In message , Paul Corfield
writes

No detail until tomorrow but a piece of wild speculation on my part is
that something to do with the signalling or power system was wrecked or
stolen [1] overnight. If it had been a relatively easy fix services
would not have been out for the time they have been. The Central Line
has been having a torrid time of it lately.

[1] I raise the stolen issue because Tramlink recently suffered theft of
parts of its electrical distribution and bonding system and that took
the network out for at least a day.

The word is that some traction current cable went 'missing'
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)