Dirty Great Machines introduces us to the might of the biggest, most awe-inspiring and technologically advanced drilling, excavation and tunnelling equipment known to man. Across the four episodes we document some of the most mind-blowing machines ever created and explore how they work. From bucket wheel excavators to monster maritime machines and mighty drills, witness these incredible pieces of equipment in action as they take on some of the world's most challenging engineering projects. In the first episode, get up close and personal with diggers burrowing below the world's cities - a massive boring machine facing the challenge of excavating Britain's deepest-ever tunnel in London and a giant mechanical worm making the earth move just metres beneath Mexico's soaring skyscrapers.