Excavating the tunnel using the Greathead shield method. This technology still in use today permitted the creation of the London tube and gave it its name. Jacks drove the shield into the clay that lies beneath most of London, the workers removed a few feet of soil, afterwhich others supported the newly created roof section and then made a brick tube.
References
Wolman, Christian. The Subterranean Railway: How the London Underground was built and how it changed the city forever. Rev. ed. Lndon: Atlantic Books, 2005.
Last modified 10 September 2004