I know, but on the big 3d picture of the construction thats on some of
the hoardings at street level, there is a tunnel between the northern
line/northern ticket hall, and the picadilly line, that joins up to the
one that currently goes from thameslink to the picadilly and the
victoria line. It would have to destroy the thameslink entrance/exit
stairs/escalators to do that, so you couldn't get from the thameslink
platforms to the thameslink station.