In this segment of Secrets of Underground London, learn about how the technical prowess of the Victorians takes underground tunneling to a whole new level with the Thames Tunnel, the first tunnel under a river being used by the oldest Underground system in the world. In an effort to provide another way for goods and people to get across the river, Marc Brunel, the chief engineer of New York, designed the world’s first tunnel under a river. He created cages to prop up against the tunnel face, giving support to the soft tunnel walls while allowing workers to excavate earth from under the riverbed. Working with bricklayers, the tunnel could then be built inch-by-inch. The workers creating the tunnel worked in appalling conditions, dealing with sewage-filled water from the Thames, fires, and a fatal flood. After eighteen years, the tunnel was completed and deemed a huge success. The clip also explores another London river, one that now runs below the city’s streets.