English: Ancient 9th/11th c. Saxon estate of Ernsborough in the parish of Swimbridge, North Devon, first edition Ordinance Survey 6" map of 1888. Text from: Humphreys, Colin, West Irishborough Farm / Rubble Hills, Chittlehampton, North Devon: Archaeological Assessment, Barnstaple, 2003, Para. 2.3 (report deposited for public reference in the Devon County Sites and Monuments Register, Exeter):

The fields around West Irishborough stand out as enclosed within a curving boundary which forms the shape of a shoe. This morphology is reminiscent of numerous other curvilinear enclosures to be found across North Devon and West Somerset (South Radworthy is a prime example). These are frequently located on or near parish boundaries and adjacent to areas of seasonal grazing. Where other boundaries address the curving "ring fence", it is apparent that the enclosed area represents land brought into cultivation, or at least enclosed, at an earlier date than that which surrounds it. A lane, often a hollow-way, following the periphery further emphasises the separate nature of the enclosure. Finally such enclosures are in most cases associated with a farm settlement or hamlet located on the periphery. By most of these criteria, it is permissible to identify the land around West Irishborough as an early enclosure. It lies on the boundary between Swimbridge and Chittlehampton parishes close to an area known as Summer Moor, there is a deeply worn track around the eastern periphery and two associated farm settlements are situated on its eastern edge. The strong suspicion exists, therefore, that Irishborough represents an early enclosure of land with an outer boundary or ring-fence pre-dating the boundaries around it. Such enclosures cannot be definitively dated but many of them appear to have been formed in the mid to late Saxon period (9th to 11th centuries)...At some point in the pre or post Conquest period settlements such as this develop a characteristic three-farm arrangement. Irishborough appears to exhibit this feature".