It should also be noted that london's postal service also deployed 2ft-wide tunnels to cart mail through the city, which was launched in the late 1920s. https:

It should also be noted that london's postal service also deployed 2ft-wide tunnels to cart mail through the city, which was launched in the late 1920s. https://en.m.wikipedia.org/wiki/London_Post_Office_Railway https://en.m.wikipedia.org/wiki/London_Post_Office_Railway