"Annabel Smyth" wrote in message

Because so much of the network was up the spout today, I ended up
changing at Waterloo to catch a northbound Bakerloo Line service to
Charing Cross.

Is it my imagination, or are the two tunnels one on top of the other
at Waterloo? And where else on the network does this apply?

You'll find instances of this on most LU tube lines.