Clive D. W. Feather wrote:

Tom Anderson writes
What might be sensible would be if preparatory work for the change was
done now - for instance, stringing catenary to Shepherd's Bush, but not
wiring it up to the mains.

Do you think it would still be there in 6 years time?

Would the people who would otherwise steal it know whether it was
switched off?

With any luck, the changeover could then be done just by setting some
jumpers in a cable cabinet somewhere, rather than having to get the
permanent way gang out again.

I would hope it would be deliberately made a lot harder than that. Do
you really want an accident waiting to happen?

That depends what "an accident waiting to happen" means. How much money
is it worth spending to avoid the combination of two very unlikely
events?

And I do not understand what the hell resignalling of the Hammersmith
and City Line has to do with this at all!
This, i have to admit, is a puzzle - how the hell is the H&C wired to
the WLL?

It isn't, but there are such things as earth leakage and induction.

I know someone involved in the electrification work on CTRL2. He has to
worry about the fact that the Underground tube tunnels, the King's Cross
station structure, the St.Pancras station structure, and the NLL all
have different values for "earth". He reckons that if he gets things
wrong, opening a breaker at Ashford could cause a lethal change in earth
voltage at the KXSP complex.

Why would a change in earth voltage be lethal?

If extending the wires is such a problem, why don't they just extend the
third rail instead? The local passenger trains would no longer need to
be dual voltage, and would therefore be cheaper. The longer distance
electric trains may still have to stop, but as they could do so while
the local trains are in the station, pathing would no longer be such a
problem!

--
Aidan Stanger
http://www.bettercrossrail.co.uk