The current Modern Railways has a free London railway map in it. For
some reason it shows a pedestrian tunnel from West Silvertown to
Millennium Dome. I was aware of no such thing, but wiki suggests that
there is a "Millennium Dome electricity cable tunnel" which can be used
by authorised personnel only. I'm wondering if this round thing ...



.... is the Silvertown end of it. I can't see anything similar on the
other bank.

The MR map does not show that there is also a pedestrian tunnel beneath
the Thames Barrier which is restricted to authorised personnel only.

--
Basil Jet recently enjoyed listening to
Bongwater - 1988 - Double Bummer (First Bummer & Second Bummer)