List of similar projects is listed here: https://en.m.wikipedia.org/wiki/London_Post_Office_Railway#Similar_railways https://en.m.wikipedia.org/wiki/London_Pos

List of similar projects is listed here: https://en.m.wikipedia.org/wiki/London_Post_Office_Railway#Similar_railways https://en.m.wikipedia.org/wiki/London_Post_Office_Railway#S... One in London is now a tourist attraction.