Longest Metro System

The London Underground is the biggest metro system in the world. It's currently undergoing a 26 billion dollar expansion project that will see its length grow to 402 kilometres long. It's the most ambitious construction project in Europe. Over a billion passengers descend into the subterranean network every year and the system, known as the Tube, has become an icon for the city of London.

This underground marvel owes its success to over a hundred years of metro engineering evolution.

It stands on the shoulders of historic engineering achievements that have allowed metro systems to grow so big. Using stunning CGI animation, this film reveals the stories of four historic inventions, embodied by landmark metro systems — giants of the subterranean world.

One by one — travelling up the scale — this film reveals the incredible stories behind these systems and the inventions that drove them ever bigger. Four ingenious leaps forward that enabled metro systems to evolve …from BIG to BIGGER into the Western world's BIGGEST.

In the first leap of technology — Tunnels — we investigate the construction of the City and South London Railway. Built in the 1880s the 6km long underground rail line called for a brand new method of tunnel boring to be invented. We reveal how engineer James Henry Greathead solved the problem with a machine that made tunneling under a city safer. In modern day London engineers use a modern equivalent of Greathead's invention but face the tricky task of tunneling under the shallow and fragile foundations of a tall iconic clock tower without causing it to topple.

In our second leap, we investigate how a new form of Propulsion was needed to power the trains traveling along the New York City Subway. In London we follow teams of engineers lowering a set of new trains down into the system, a task which requires pinpoint accuracy. In the third leap of technology we reveal how metro system engineers at the Paris Metro learned how to create vast subterranean Stations. We see how engineer Fulgence Bienvenüe learned how to sink a station into the soft earth alongside the River Seine like a giant submarine. Today in London engineers are facing a similar challenge alongside the River Thames where they must build the new stations for the Metro's Crossrail line in watery docks.

Finally we explore how engineers at the London Underground keep metro systems safe by installing systems to protect passengers in the event of a fire.

Featuring interviews with engineers working on the London Underground and combined with practical demonstrations this film provides the ultimate explanation of how ingenious technology enabled the metro system to evolve into the huge subterranean network that is the London Underground.

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