The earliest fields are usually called ancient enclosures, to distinguish it from the land enclosed in the 18th and 19th century under Parliamentary Enclosure Acts. Such ancient enclosure tends to be on the poorer soils, but not exclusively. The key factor seems to who owned the manor. Almost all the early enclosed townships were the centres of estates and many had, or later acquired, large country houses. Some were monastic manors, as at Pipewell, Fineshade, Biggin and Thorpe Underwood. Others were royal manors or held by the nobility or lesser landowners, as at Fotheringhay, Boughton and Kirby. However, the presence of an estate centre and country house did not guarantee that early enclosure would take place. Rockingham had its castle but was not enclosed until 1809.
Anciently enclosed land in the early modern period
The large early enclosures, mostly established as great sheepwalks, were later subdivided and occasionally even replanned as the agricultural economy changed and agricultural practices evolved. It is therefore rare for early boundaries to survive unchanged, but at Dingley early fields do survive with little or no later infilling. In Brigstock the opposite is true, for the Great Park, enclosed from the forest in the early 17th century, saw a great deal of later subdivision, though again most of these boundaries still survive.
Early enclosure did not necessarily encompass the whole of a township. There are many examples in the forest of piecemeal enclosure. This could take the form of small closes scattered throughout the open fields, as at Gretton and Kings Cliffe, or the enclosure of a single medieval field, as at Braybrooke. However in the heart of the forest small areas of these enclosures on the woodland edge can be shown never to have been part of the open fields. Some of these are known to have been enclosed as assarts, that is directly from woodland within the forest, during the great expansion of agriculture before 1300. Where the boundaries of these assarts remain today they represent a very rare survival from the medieval landscape.