On 5 Feb, 19:29, wrote:
I've just spoken to my father about this, so I've now got some more
accurate information, assuming his memory's still reasonably accurate,
and I can interpret his doodles the right way.
Thanks, its very detailed.

Like most underground lifts, there was a parallel passage on the other
side for people heading in the other direction....
except that during WWII it was converted into a shelter.
Did they do that at other stations with long disused passages?

stretches far enough to go over the southwest end of the westbound
platform (so it must be the jutting out bit in the ceiling at that
end)
I've been wondering what that was for ages. Maybe the steps inside the
cupboard up there must lead up there.

The northern-line branch of the tunnel, in addition to joining up with
the lifts, also had a turning for a passage that joined up with the
northern line emergency stairs. ...
Perhaps this was one of those idiotic
"well, that's what it says in the act of parliament, so we'll have to
build it" things, like the aldwych branch - its academic now as this
branch is mainly cut off by the northern line escalators.
Maybe they built it because they were planning to block up the older
route to the stairs?
Your description suggests that the northern line lifts must be about
one floor below the northern city line level, so the old access route
to the emergency stairs should be about the same level as the northern
city line (on account of the bridge to take it across the lift lobby);
so maybe the extension of the northern city line south would have cut
through it, hence the reason for needing a new route to the emergency
stairs.

when they started the extension south, they re-built the lift lobby
one floor higher up
Why were they so short sighted when they built the original lobby?

Not quite accurate. The stairs do wrap round either side of the lift,
but these were always accessed via steps through the headwall at the
end of the platform - they still are (sort-of, see above), but you
can't see the access point because there's a "modern" cabin placed
immediately in front of it on ...
On platform 9? I think I know what you mean, but what's the "cabin"
there for?