"Paul Scott" wrote

Was a grade separated Metropolitan Junction a fall back proposal if four
tracking through Borough Market proved impossible?

IMHO the whole Thameslink Project collapses if 4-tracking from London Bridge
to Metropolitan Junction proves impossible. Charing Cross needs best part of
30 tph in the peak, and Thameslink is based on 16-18 tph via London Bridge
in the peak, and you can't run 46-48 tph on one track.

Peter