In message , Richard J.
writes

Small matter of electrocution perhaps? My point is that if Greenwich is
meant to burst into life with its fast-start gas turbines, doesn't that mean
that traction current can be restored in a matter of a few minutes?

I'm not sure it does. According to the "Emergency Supply Plan" for
London Underground on the Seeboard PowerLink website:

To allow all the Underground's power supplies to be taken from
the National Grid - Powerlink successfully completed a project
prior to the closure of Lots Road. This included the
installation of battery inverter units for emergency lighting
and other essential supplies in control rooms and sub-surface
stations together with the refurbishment of generating units at
Powerlink's Emergency Power Station providing power for
essential pumps, deep lifts and escalators.

No mention there of Greenwich being able to supply traction current, but
merely power to help evacuate the system and stop it flooding.

--
Paul Terry