"Patrick" writes:
... I wonder if it'd be possible to carve out a new station UNDER
the Thames, called "Wapping & Rotherhithe" which you could enter
& exit on both sides of the river?

Paris has a station like that%, but the Thames is wider. The length
of tunnel between Wapping and Rotherhithe is about 1,200 feet, which
would make rather a long station for urban trains.

Also, the existing tunnel was built with *great* difficulty because
preparatory bores were misleading and it was built too close to the
riverbed. Of course, this was the first tunnel ever to be built
under a river and technology has advanced since then... but I'd think
that building a station at the depth of the present tunnel is something
that engineers would shrink from even today.

% St-Germain - Notre Dame on RER Line B.
--
Mark Brader "If you design for compatibility with a
Toronto donkey cart, what you get is a donkey cart."
-- ?, quoted by Henry Spencer

My text in this article is in the public domain.