Tower Subway

The Tower Subway is a circular tunnel beneath the Thames in central London. It runs between Tower Hill on the north bank and Vine Lane on the south. In 1869 a 410-metre tunnel was dug through London clay using a Greathead shield. The shield was a circular iron device that kept the tunnel stable as it advanced. Peter Barlow had patented a similar idea in 1864, but never built it. Greathead improved the design and completed the work in fourteen weeks. The tunnel opened as a cable railway in August 1870. A small wooden carriage carried up to twelve passengers at a time, pulled by steam engines on each bank. The service charged a penny or two pence for first class, but it lost money and closed within months. In December 1870 the tunnel reopened for pedestrians at half a penny toll. A million people used it each year, mostly workers who had relied on ferries. Visitors today walk through the narrow brick-lined tube lit by rows of lamps. The walls feel damp and the floor has a slight give underfoot. The spiral staircases at each end lead down to the tunnel mouth. The air carries echoes of footsteps and voices from the opposite direction. The tunnel’s iron lining curves overhead like a great intestine beneath the river.