In message
, at
12:38:57 on Sat, 18 May 2013, PhilD remarked:
A round Circle Line would be a separate project, though I suspect it
would make the outskirts rather messy.

On that diagram it would have no effect on the outskirts, the worst it
might do is introduce some extra kinks in the Northern Line between
Kings Cross and Monument.
--
Roland Perry