Greathead Tunneling Shield

With the London Underground's continued expansion, Bank and Monument stations have been interlinked to form one giant station. Connecting 5 different underground lines, the combined station is one of the busiest on the entire network, with tens of thousands of commuters passing through every day.

Keen-eyed individuals making the interchange between the Waterloo & City and Docklands Light Railway lines will notice a red cast iron band standing out against the interlinking passageway's neutral colour scheme. Remarkably, this was part of the Greathead Tunneling Shield, used in 1898 during the construction of the original Waterloo & City line.

This particular style of tunneling shield was named after its inventor, the South African-born engineer James Henry Greathead. His cylindrical, single-piece design enabled tunnels to be easily and safely carved through the layer of clay beneath London.

Abandoned 18 metres below ground after the original tunnel was completed, the shield lay dormant until 1987, unearthed during the construction of the new Waterloo and City Underground line. Incorporated into the passageway's design, it is passed by thousands of passengers per day, and millions per year walk through the shield, completely unaware of its significance. Modern tunneling practices still rely heavily on Greathead's principles, while the circular-shaped tunnels carved out by these machines contributed to the London Underground's colloquial nickname of 'The Tube'.