No mound, no wall, no visible trace of anything human. Yet from the air, the cropmark tells a different story: a D-shaped enclosure pressed into the soil, invisible to anyone walking the field but legible, in the right light and the right season, as a faint ghost of an older arrangement of space.

The enclosure came to light in a photograph taken on 16 July 1971 as part of the Cambridge University Collection of Aerial Photography, reference CUCAP BGG029k. Cropmarks of this kind appear when buried features, such as ditches or foundations, affect how vegetation grows above them. A fosse, which is simply a ditch dug as part of a boundary or defensive arrangement, retains moisture differently from the surrounding soil, and the crops above it respond accordingly, growing slightly taller or greener. Here, the eastern side of the enclosure is defined by a straight-sided fosse running approximately 35 metres, from which a curvilinear fosse extends westward, forming the rounded portion of the D-shape, with a diameter of roughly 30 metres. The land is under tillage, which both helps preserve the buried features from disturbance by livestock and, in dry summers, creates the very conditions that make cropmarks visible from altitude.