A loose jambstone was found in the graveyard of the 15thc. church in Killyleagh. It was discovered by Dudley Waterman in the late 1960s following clearance of the graveyard. Although the jambstone was placed in storage at the time, its current location is unknown. Waterman published a brief report on the jambstone in 1971, including a drawing and photograph (Waterman 1971). A cross-inscribed stone is the only other indication of an early Christian settlement at Killyleagh. An image and diagram of the jambstone is found in Waterman's article, and reproduced here with the kind permission of the Ulster Archaeological Society.

Little is known of the history of the site. The current church is entirely 15thc.

The animal head mask is an unusual type in an Irish context, although it has French parallels. In Calvados, at St Contest a similar head is found on the inner arch and jambs of the W door, and at St Vigor in Authie another parallel is found on the arch of the S doorway. Both are dated to the second half of the 12thc. A late 12thc. date is suggested for the Killyleagh head.