In article .com,
(TheOneKEA) wrote:

Clive D. W. Feather wrote:

However, the presence of the
trailing crossover was deemed to be too useful to the line, so
instead of filling in the original NB tunnel north of the
divergence, a step-plate junction was built.

It would have been normal practice to build a step-plate junction
in any case, even if the old line was going to be abandoned. See
London Bridge and Angel for examples.

True. I may have been a little unclear there; the step-plate junction
itself would have _always_ been built, but the tunnel beyond would have
been out of use and maybe filled in a short distance from the train.

although this is normally the case, there are the odd exceptions, usually
due to geographical constraints

One example is at the north end of the SB diversion at London Bridge.
Here, the original NB tunnel was filled in and then the diversion dug
through it. There being insufficient clearance (I think it was something
to do with the foundations of the old London Bridge (as in bridge, not
station))in order to construct the step-plate. The southern end of the
diversion was a standard step-plate. The advantage of a step-plate
junction is that it can be built around the existing tunnel and trains can
continue to run during construction.
see:
http://www.romilepa.pwp.blueyonder.co.uk/ZTemp/
for a picture of the step-plate under construction

* - the other one was a planned connection between the Bakerloo
and the CCE&HR extension between Waterloo and Kennington; later
it was downgraded to a non-track connection, and then later
forgotten. I could be wrong about this though.

The original plan was for a Camden-style every-way-possible junction,

with both Northern and Bakerloo trains running to both Morden and
Camberwell. I'm not sure what you mean by "non-track connection"
(non-passenger connection, perhaps?) but I'd not heard that bit
before.

Now that is something I'd not heard before! Do you have any more
information?

As for the non-track connection, an AET who works on the Bakerloo line
says that you can hear the Northern line when standing in the Lambeth
North scissors cavern; IIRC he speculated that the closeness of the two
lines would have made it easy for a foot connection of some kind. But
as I said, I could be wrong.


The Northern Line also has a traction current feed from the Lambeth North
substation to the CX branch, so there's probably a tunnel between the two
anyway.

Roger