In message , Roland Perry
writes

The report I saw said the grid fault was at Wimbledon. Is it possible
that most of the Underground's power is brought in that way - it would
plumb into the existing wiring from Lots Rd rather easily.

I don't believe so - in fact traction current on the District's
Wimbledon branch is supplied by Railtrack, IIRC.

When plans for closing Lot's Road were drawn up it was stated that there
would be three bulk supply points on the National Grid for London
Underground, any two of which could keep the system running if there was
a failure - so I guess at least two supply points must have failed.

(The effects of the power cut seemed to be very localised - we live only
2 or 3 miles from Wimbledon and were not affected at all).

--
Paul Terry