The tiny roofless oratory, known as the Priests' House, lies to the SW of the cathedral. Its internal dimensions are 4.40 m by 2.33 m. There is a narrow door in the S wall and a curious blind arch in the E wall, the latter decorated with Romanesque ornament. As Leask noted, except for the first two or three courses of masonry, the structure is a restoration. Unfortunately the Office of Public Works based their reconstruction in the 1870s on Beranger's drawing of 1779, which did not give an accurate impression of the medieval building.

The function of the building has occasioned much argument. The colloquial name is not medieval in origin and is said to relate to the burial of clergy in or around the building in relatively modern times. Some authorities have claimed that the chapel was the burial place of St Kevin, others have described it as a mortuary chapel.

The 'lintel' stone has been the source of much confusion and argument. It was first recorded by the 18thc topographical artist, Gabriel Beranger, who drew the stone intact and gave it a triangular head. His drawing is inscribed 'Stone found on the ground at Priest church'. Beranger's drawing was copied by subsequent artists and it is not clear whether it was really intact at the time or whether he reconstructed the lost portions. The problem is discussed at length by both Barrow (34–6) and Moss. Given the slight curvature of the upper surface, it is possible that it functioned as a small tympanum. However, tympana are rare in Ireland and none has a figural subject of this type. If the stone was once triangular in form, it might have formed the end of a shrine or sarcophagus. Others have suggested it is a fragment of the base of a high cross.

In 1842 the stone was lying in a local farmyard and it was probably not set in place in the Priests' House until the 'restorations' carried out by the Office of Public Works in the 1870s.

It is by no means certain that the carving is Romanesque in date. Figures carrying bells and crosiers are found on a number of early crosses and slabs, for example, those at Kinnitty (Offaly) and Killadeas (Fermanagh). The latter provides a telling comparison. If it was carved in the 12thc, the style was very traditional.

The blind arch in the E wall was reconstructed in the 1870s, but as Rachel Moss has persuasively argued, it was almost certainly a concoction of the 18thc, using stones from a destroyed window (or windows). The radii of the individual voussoirs suggest that they come from two or even three different arches. When Beranger drew the arch in 1779 the rear wall was apparently built up against it. He commented: 'The front entrance built up latterly with stones in part'. Beranger also drew the capitals in an intact form, showing human heads on the angle and long hair extending into interlace. Again it is unclear whether these capitals were really intact at the time.

The stones clearly come from an unusually ornate rear arch or series of rear arches; to judge from the angle rolls with their row of recessed beading, a date of 1165–70 is probably the earliest that could be considered and they may be considerably later. There is no evidence to suggest the original location of the window(s): the arch is too broad for the Priests' House and, as the stone is not yellow oolite, it is unlikely to come from the chancel of the cathedral. Were the stones associated with St Saviour's Priory?