In message .com,
Boltar writes

Did moorgate station have to be completely rebuilt? If not how
did they get the new tracks into alignment with the old platforms
in such a short distance?

Although the line had to be sunk, the lateral deviation was really quite
slight, simply straightening a slight kink in the original line's
entrance to Moorgate, which you can see in the following photo:

http://www.barbicanliving.co.uk/imag...dsiteplan1.htm

The following URL shows both the original line and the deviation (which
runs pretty much underneath the two lakes):

http://www.barbicanliving.co.uk/crea...ay_cutting.htm

As you can see, the approach to Moorgate was only minimally affected,
although I guess there could have been some slight realignment at the
outermost part of the platforms.

--
Paul Terry