That's Camden Junction, which is not part of the station. The axonometric drawings exist for fire safety reasons AFAIK -- similar drawings are usually displayed somewhere in the ticket hall -- so details of the tunnels are out of scope.

(1927 drawing of the junction on this page: http://districtdavesforum.co.uk/thread/6095/camden-town-junc...)

I like that it's a non-blocking switch. There are alternatives which would restrict concurrent traffic between any two branches.

For a 2D version, showing a track diagram for the whole London Underground network, there's an excellent map:

http://carto.metro.free.fr/cartes/metro-tram-london/