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

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-junction 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.