On Wed, 16 Apr 2014 13:45:26 +0100, Roland Perry wrote:
In message , at 13:31:24 on
Wed, 16 Apr 2014, Paul Corfield remarked:
It is dealing with the damaged tunnel lining between Baker St and Bond
St. The tunnel rings are being slowly replaced in a series of
engineering possessions.

Any information on what caused the damage?

http://www.nce.co.uk/news/geotechnic...648457.article
says
"The primary cause of the damage was clay shrinkage in the
ground around the tunnel, LU principal tunnel engineer Keith
Bowers told NCE. Other factors, including probable issues with
the quality of design and construction, are thought to have
worsened the problem."

The full article is subscription only but if you paste the URL into
Google and then click on the search result you can read it all.