Nikki Smith wrote:

RBKC are the original sticklers for checking that basements are
constructed correctly. They were the first to insist on full BIA
reports to be included in the planning documents, and there is one
for the work to No 4. Looks like the new basement required double
underpins and resin grouting of the gravels to keep it temporarily
watertight. Must have been pretty expensive!
Yes looks like No 4's sub-basement probably isn't blame for No 3
collapsing. No 2-3 also had permission to extend basement to the rear,
but also shows a lot of removing internal columns and walls, also
removing beams and concealing them in floors above, installing lift shaft