However I can't pretend to understand what's going on there at the moment and will let Chris tell the story:
"London Underground are shutting the interchanges at the Bank/Monument complex from the 31st of March for over a year. No more interchanges between Bank and Monument at all, and within Bank, interchanges between DLR / Central / Northern / Waterloo & City are severely limited, by the looks of things:
This is especially bad for people who use the DLR (like me) - the DLR/Central Line escalators have only just fully reopened after being in restricted service (only an up escalator rather than both directions and so lots of overcrowding) since last summer for maintenance work, so all that was for nothing. And from June 2008 till April 2009 Tower Gateway is shut for expansion works, so Bank will be the only station on the DLR in central London so it'll be even more crowded - and you won't be able to change onto any other line apart from the Northern Line once you get there.
I'm mystified as to why they've timed this like this - it's going to be really inconvenient for anyone trying to come into central London on the DLR without diverting via Canary Wharf & the Jubilee, and I'm especially annoyed we've only been given 11 days notice for what's over a year of disruption.
Anyway, I know maintenance needs to be done but this looks really badly managed from my point of view."
If anyone has any views as to why they've done it that way please make yourself known in the comments.