Alongside them, human faces emerge from the capitals of a banded shaft where two late 13th-century windows meet internally, their arches differing in shape, one rounded, one bluntly pointed, though they share the same embrasure. The whole arrangement is partly obscured by a belfry tower that was inserted into the west end of the church during a later phase of building, its four masonry piers rising to eaves level and its southwest pier containing a spiral stair. It is an oddly layered piece of architecture, medieval pragmatism and craft occupying the same wall.

The priory was founded in 1229 by Philip de Barry and dedicated to St Thomas Becket. It belonged to the Augustinian order, a congregation of canons who followed the Rule of St Augustine and were a significant presence in Anglo-Norman Ireland. The community here sat in flat pasture roughly two hundred metres south of the Awbeg River, and the complex that survives is substantial: a church over fifty metres long, a cloister on its south side with ranges extending to the south, west, and east, a four-storey rectangular tower added in the late-medieval period against the north end of the west claustral range, a separate rectangular tower some seventy metres to the north, and a columbarium, a circular dovecote, about twenty-five metres to the southeast. A fish-pond known locally as Monk's Pond lies roughly five hundred and fifty metres to the northeast, and a clapper bridge over the river to the northwest is also thought to have served the priory. The community was dissolved in 1541, possibly re-established for a time, and by 1750 the buildings were already described as ruins. For a period stretching into the early twentieth century, a farmhouse and outbuildings occupied the centre and west end of the church itself.

The cloister retains some legible detail. On the east side, the base of an elaborate two-metre-wide doorway survives, identified as the entrance to the chapter house, the room where the community would gather daily for readings and administrative business; its jambs preserve the bases of three rounded engaged pillars on each side with filleted moulding at the inner edges. A vaulted passage runs south from the southeast corner of the cloister walk, and a low wall at its far end is likely the base of the refectory's south wall. The stone shelf in a masonry block at the southwest corner of the cloister is thought to be the remains of the laver, a washing basin where canons would rinse their hands before meals, repositioned here at some point by the OPW. The southeast corner of the church still stands close to its original height, preserving window details and fragments of banded shaft, and three semi-circular recesses in the south wall nearby may be the remains of a sedilia, a set of seats used by officiating clergy during the liturgy.