It is not the main event, architecturally speaking, but that secondary status is precisely what makes it worth attention. Annexes of this kind are comparatively rare survivals, and this one has held its shape well enough that birch trees have had time to colonise the raised interior, lending it a quietly enclosed character that the surrounding earthworks only reinforce.

The feature is classed as a moated annexe, meaning it functioned as a subsidiary enclosure attached to a moated site, the kind of arrangement associated with medieval manorial settlement in Ireland, typically from the thirteenth and fourteenth centuries. A moated site, for the unfamiliar, consists of a raised platform surrounded by a water-filled or wet ditch, and was used by Anglo-Norman settlers and others as a form of enclosed farmstead or minor residence. Here, the annexe adjoins the northern half of the moated site's western side, sharing its eastern fosse, and measures roughly 11.6 metres east to west and 11.3 metres north to south. The surrounding fosse is four metres wide and still wet, with a depth of around 1.2 metres, while a low counterscarp bank, the outer lip of the ditch, survives in fragments along the southern and western sides and a short stretch of the north. What is particularly useful is that the enclosure was already visible and distinct enough to be recorded on the Ordnance Survey six-inch map of 1842, where it appears as a hachured square, the cartographers' way of indicating a raised or scarped feature on the ground.