Overview: Tony Robinson and geophys boffin John Gater look back over 200 digs at the extraordinary achievements of cutting-edge geophysics technology, which has uncovered lost Roman villas, tombs, temples and ancient monuments, as well as a host of old broken tractor bits and enigmatic ditches. The science of geophys has changed out of all recognition: 20 years ago the team huddled around a dotmatrix printer as it slowly produced a geophysical picture of an abbey hidden underground; now they can produce complex three-dimensional images of whole buildings within minutes. In an effort to finally understand what geophys actually means, Tony buries 10 objects in a field and challenges John to use his technological arsenal to identify them all, without digging. Can geophys now tell the difference between a bicycle and a toilet?