David Baxter wrote in message ...
Also, purely out of curiosity, what -do- all those thick cables do? I always
assumed tube trains were hooked up to the power and negative tracks.


Depends which cables you mean really - the *really* think black ones are the high tension ones which deliver AC at 11kV from the Bulk Supply Point to the substations, from where it is transformed and rectified to 630vDC for supply to the current rails.

The rest serve a range of things including lift and escalator supply, lighting, telephones, clocks, signalling, train radio leaky feeder etc. It's not uncommon also for many of the cables you see to be redundant.