The old church of St. Begnet sits in the churchyard on the north side of Castle Street, across the road from the Church of the Assumption. The surviving remains date from the thirteenth century but there is some evidence for an earlier twelfth century building. The church was extended eastwards in the fifteenth century during Dalkey’s period of prosperity. It was further embellished in the sixteenth century when the two light round headed windows were inserted.
In the Middle Ages the parish of Dalkey was served by a chaplain appointed by the Prior of Christ Church Cathedral, Dublin, to whom the parish belonged. Following Henry the Eight’s Reformation the church was converted to Protestant use but it lost its Catholic congregation. It was reported in the early seventeenth century that the only worshippers at Sunday service were the Minister’s family and English and Scottish fishermen during the herring season.
The Protestant Archbishop Bulkeley recorded in his 1630 visitation that the chancel had lost its roof. The building ceased to be used for public worship and gradually became the picturesque ruin we see today.