A short distance from the centre of Cambridge, sandwiched between the M11 motorway and Girton College on the Huntingdon Road, a 22-tonne mechanical digger and a dozen men and women in high-viz vests are working a field under a big East Anglian sky. The stubbled soil is criss-crossed with dozens of short, shallow trenches dug to a mathematical pattern; from the air, it must look like the board for some giant, fiendishly complicated parlour game. In fact, this is the site for most of Cambridge University's future growth: soon this 120-hectare field will house research and development facilities, academic buildings, accommodation for 1,500 university staff and 2,000 postgraduates, 1,500 private homes, a school, shops and public open spaces. Right now, however, it's an archaeological dig. Or, more accurately, an archaeological evaluation. Obligatory – in theory, at least – for all major new developments since 1990, the procedure is aimed at establishing roughly what might lie beneath any proposed new buildings, and whether more exhaustive excavation might be desirable or necessary. [...]