Cropmarks of an irregular curvilinear enclosure, lying close to a series of other cropmarks, have been recorded in this location on a number of occasions. During the drought summer of 2013, new Royal Commission aerial reconnaissance on 29th July 2013 clarified the layout of the monument complex with the new cropmarks suggesting the existence of a previously unsuspected Neolithic causewayed enclosure. This would be the second such enclosure in Pembrokeshire, after Banc Du at New Inn (NPRN 308024).

Following air photo mapping by T. Driver in November 2015, the Dryslwyn enclosure measures 115m diameter and encloses 1.06 hectares. Most of the site enclose a level, or gently sloping, hillside but the south-western sweep of the enclosure runs over the lip of a steeper slope while the south-east side abuts a scarp edge; no indication of the enclosure ditches can be seen on this side and it may be that no enclosure was required here.

The causewayed nature of the enclosure is evident in its variable circuit. Only two partly bivallate sections are visible on the north-east and north sides while the remainder of the enclosure is univallate. There are three formal gateways visible: On the north-east there is a simple entrance gap flanked asymmetrically by partly bivallate enclosure ditches on the south-east side only which run for a short distance. On the north-west side is a second gateway, this time with out-turned terminals flanked asymmetrically by a short length of bivallate ditches on the west side. On the south side is a third gateway, defined by one out-turned terminal and one simple terminal in the manner of the Norton, Ogmore enclosure (NPRN 90000) and possibly that at Flemingston (NPRN 404651). At least one other simple, narrow gap can be seen on the west side between causewayed ditch sections.

The enclosure is crossed in the south-west part by parallel ditches of a ploughed out historic boundary. Within the south-eastern part of the interior, against the steeper scarp edge, are cropmarks of two very large quarry pits.

The enclosure lies just south-west of a pear-shaped defended enclosure of Iron Age type (NPRN 309488) with a pair of plough-levelled round barrows some 88m to the north-east, the eastern barrow being particularly large (approx. 33m diameter; NPRN 309487).

The enclosure was excavated during Easter 2015 by Geoffrey Wainwright and Tim Darvill and students of Bournemouth University. The excavations were overflown and recorded during RCAHMW aerial reconnaissance on 15th April 2015.

T. Driver, RCAHMW, 2015