Pylons and cables carry electricity through the countryside, but in cities there is no space for pylons and cables. In the city of London there are 29,000km of electrical cable buried underground. If all these cables were put end to end they would stretch to Australia. There are lots of underground substations all over London. These contain many switches and each one controls the electrical supply to specific places and famous monuments.

First broadcast:
15 October 2007

This clip is perfect for clarifying with children how electricity 'mysteriously' appears in homes, shops, other buildings and public spaces. To help children to grasp the concept, children could use boxes and simple circuits to create a 3D model town with underground wiring and sub-stations.