Laura-Ann wrote:

On my way, about two weeks ago, somewhere between London Bridge and Waterloo
East (I think it was those two stations, if not, then Waterloo East, and
Charing Cross), the train went over a bridge which crossed a road. As it
went over, I looked down, and saw some large gray walls that were shielding
something (possibly a construction site?), and on the walls was printed:
"LONDON UNDERGROUND EXTENSION", with the usual Underground Roundel.

Have I missed something - is there genuinely an extension being built in
that area, or were the walls just being used to hide some construction
because those were the only walls they could find?

Thanks
Laura-Ann

Nope - they're just leftovers from the Jubilee Line extension which did
use this bit of land.

I think they may be planning on using the plot if they finally build
Thameslink 2000 which is why they haven't sold it yet (which would
probably be worth quite a few quid).