Lapsed Historian

Telephone cable tunnels had also been dug between various government buildings by 1940, but despite this the pneumatic tubes were still intensively used for sending documents, plans, and maps.

It is not known how long these government tubes were used after the war, but some may still be in service today, as they are secure, unjammable, and not susceptible to electronic eavesdropping or electro-magnetic interference.

Look at that. It’s not a big truck. It’s a series of tubes.