Only fragmentary traces remain of what was once the middle unit of three conjoined cells, its walls now little more than low scatterings of earth and stone. That it existed at all is known largely because someone thought to measure it before it disappeared entirely.

The antiquarian Thomas Johnson Westropp recorded the structure in 1911, noting that it formed the second of three adjoining cells set within the interior of a promontory fort, a type of enclosure in which a headland is cut off by one or more earthen or stone ramparts across the neck of land, using the sea cliffs as natural defences on the remaining sides. Westropp described walls of earth and stone between roughly 0.9 and 1.2 metres thick, an internal width of approximately 3.6 metres, and a surviving height of only about 0.3 metres even at the time of his visit. The cell adjoined the fort wall itself, suggesting it was integrated into the wider defensive or domestic arrangement of the enclosure rather than added as an afterthought. No date has been established for the structure, and the sparse physical evidence remaining makes it unlikely that one ever will be.