In message , at 12:12:18 on Sun, 13
Jan 2013, tim..... remarked:
Changing at Green Park is okay as long as one always changes by going
up to ticket hall level and back down.

Yes, and changing at Warren St is a bit like that too.

no, you only have to go to the "half" landing.

That's why it's "a bit" like Green Park, not identical.
--
Roland Perry