This rectangular enclosure, measuring approximately 110 metres on each side, has been a fixture on Ordnance Survey maps since 1842, though its appearance has changed considerably over the centuries. While no local tradition explains the origin of its monastic name, the site’s defensive earthworks tell their own story of ancient occupation and subsequent agricultural adaptation.

The fort’s defences remain most visible along its eastern and southern sides, where an earthen bank rises about a metre high on the interior, accompanied by an external fosse, or defensive ditch, that originally measured just over a metre deep. Time and farming have taken their toll on the western and northern boundaries; only a slight scarp along the southern half of the west side and a low rise at the western end of the north side hint at where the defensive circuit once ran. The eastern bank has been breached with a four-metre-wide modern break, complete with a concrete bridge spanning the fosse, located 19 metres from the southeast corner. Interestingly, what P.J. Hartnett identified in 1939 as the original entrance with causeway at the centre of the eastern bank has since been blocked by a narrower section of bank measuring seven metres long.

The southern defences showcase both preservation and adaptation, with 64 metres of the bank surviving beneath heavy bush cover, incorporated into the modern field fence system, whilst the remaining 20 metres have been completely levelled. The fosse here extends for 76 metres and, like much of the surrounding ditch system, has been recut from its original depth of 0.7 metres to 1.6 metres to serve as agricultural drainage. Inside the grass-covered enclosure, a natural rise in the southwest quadrant features exposed rock outcropping, adding to the site’s defensive advantages. Hartnett’s 1939 survey recorded additional features now lost, including a fosse enclosing the western side with a causeway about 20 metres from the southwest corner, as well as bank and fosse defences along the northern perimeter.