To settle an argument I’ve been having for ages, I was looking for a diagram which illustrates what happens to the Northern line at Camden Town. The tube map doesn’t show the details. Wikipedia’s Northern Line article has schematic strip diagram (down the right), which shows where the junction is [UPDATE: since then the wikipedia Camden Town article also has a more detailed diagram on the right]
This prompted a whole fresh bout of web surfing around [useful/strange modifications to the tube map] (owen.massey.net/tubemaps.html is a broken link now). (hmmm I need to suggest a new addition. The OpenStreetMap tube map is the only truly open licensed tube map)
But ultimately the most comprehensive diagram of what really happens below the streets of Camden, came from asking the tube enthusiasts on wikipedia. Actually all the underground diagrams on this very old ‘see how they run’ website (an archived copy of an old geocities website!) …are interesting for Londoners to puzzle over. It’s weird how you can go through that kind of underground train junction every day, and not really have any understanding of its layout.