About this programme

One-off documentary charting four of the main technological advances that have helped make the Tube the second biggest metro system in the world, including tunnel-boring methods developed in the 1880s and a new form of train propulsion invented for the New York City Subway. The programme also reveals how the Tube owes a debt to the engineers at the Paris Metro for their subterranean station designs, and the safety precautions that are in place to protect passengers in the event of a fire.