We meet the bucket wheel excavators. Their mission is to peel back the surface of the earth with each turn of their colossal parts.

Man's desire for natural resources is insatiable, whether it is to power our homes, fuel our cars or build our skyscrapers. But with reserves on land running dry, we are now looking to the oceans to satisfy the needs of 21st century living. This programme showcases the cutting-edge machines at the forefront of this assault.

In Canada, almost two miles underground in the world's deepest copper and zinc mine, a mighty drill chews through rock, digging deep holes which are then filled with explosives and detonated, leaving behind debris packed with valuable minerals. Meanwhile in Helsinki, Finland, cameras follow a mission to excavate a new metro tunnel to improve commuter services - but working seven metres beneath the bustling city calls for precision engineering and one false move could lead to disaster. Plus, a mining machine works continuously underneath the Cheshire countryside to keep Britain's transport network moving. Last in the series.