Dave Arquati wrote in
:

The only way I can think of making it more intuitive is to use
"citybound", or perhaps to highlight Zone 1 stations on the line
diagrams. Then again, using citybound would probably add new
confusion, and it would only work for non-central stations.

Especially as "The City" means one thing to those who live and work in
London and something completely different to tourists, who usually use it
to mean "the central area where all the stuff is I want to see", or in
other words the West End.

Iain