On a summer's day in July 1989, an aerial photograph captured what are known as cropmarks, the differential growth patterns that appear in cereal crops when buried features affect soil moisture and nutrients. What emerged in that image was the outline of a field system: two parallel boundaries running east to west, separated by roughly 35 metres, with a third boundary running north to south, possibly extending from the northernmost of the two east-west lines. As that north-south boundary continues upward across the photograph, it appears to curve gently westward, suggesting the kind of organic, hand-laid boundary rather than anything imposed on a grid.

Cropmarks are one of archaeology's quieter revelations. They appear and disappear with the seasons, visible only when crops are at the right stage of growth and the underlying conditions are favourable, which is why a single aerial photograph taken on 13 July 1989, catalogued as GB89.Q.29, carries so much weight. The field system at Warrington has not been excavated, so its age remains unknown. Two enclosures were also identified as cropmarks in the same area, lying immediately to the north and north-east of the field system boundaries, though their relationship to the field system is uncertain and the features are not necessarily from the same period. What the photograph preserves is a moment when the past briefly announced itself through the medium of growing grain.