Reading about The Earl's Court Christmas blockade the thought occurred to me, at which depots are the D Stock currently maintained? Are they all based in one so that only one depot team need to keep the knowledge/parts, or are they based at both ends of the line so that in the event of a problem they can be put away anywhere?
Most of the routine maintenance is still done at Upminster. Exam, battery maintenance and possibly door maintenance are regularly done there. Also any faulty d stock that happens to end up at Upminster will also get fixed there. I'm not sure if Ealing still do shed day, but the other routine stuff like program lift and planned machine changes would surely have stopped as the trains are running down