As we've seen before, the 1920s and 30s were the heyday of cutaway diagrams. Newspapers and magazines commissioned striking illustrations, depicting cities, structures and battlefields in three-dimensions.
London's complex subterranean systems were a favourite topic. Here, we dig out four more examples from the newspaper archives.
1924: The tunnels of Piccadilly Circus
Piccadilly Circus station was completely remodelled during the 1920s. The engineering works resulted in the exile of the Eros statue to Embankment Gardens. Here we see the pleasing symmetry, not only of the new subterranean concourse, but also of the tunnels and escalators.
1924: Building the Post Office railway
London once had a private tube system, used by the Post Office to move parcels across the city. Here we see a cutaway from 1924 that explains how the trains were loaded and unloaded. Unlike London Underground, the system made use of the hidden part of the cylindrical tunnel, below the track bed.
Part of the system is, of course, now open as the MailRail visitor attraction, part of the Postal Museum in Clerkenwell.
1926: Waterloo's new underground platforms
Like a drawing by MC Escher, the tunnels and undercrofts beneath Waterloo station defy casual understanding. This cutaway shows part of the works to connect the Northern line between (what is now) Embankment and Kennington — a section of line that only opened in 1926.
The chief feature is the three-track escalator, which was threaded between existing piers with a leeway of just two inches on either side. All this decades before computer modelling and modern surveying techniques.
1939: Bomb-proofing the underground
With the threat of air raids imminent, London Underground looked at ways to protect the tube network from aerial bombardment. A direct hit on a line under the Thames would have been catastrophic. To this end, giant floodgates were put in place that might contain the river water in the event of inundation. Pity anybody trapped in the middle.