One of the three live LNSs just restarted.
We are investigating.
I looks like the backup systems kicked in within seconds as planned.
Many lines have correctly fallen back to D.gormless. They will be moved over night back to B.
Lines have reconnected cleanly as per the contingency plans. We have to find the cause, but I'll close this major issue for now.
(Graphs would have been lost for the day, sorry)