Embedded in the fabric of an eighteenth-century church in Waterford city is a wall that quietly refuses to belong to it. The western wall of St Olave's, stretching almost ten metres, is medieval masonry, and set within it is a blocked pointed doorway, the kind of narrow Gothic opening that dates the stonework to a period long before the building that now surrounds it. Most visitors to the church see a Georgian structure. What they are partly looking at is something considerably older.

The dedication gives the game away. Olave, or Óláfr, is a Norse name, and churches bearing it in Ireland tend to cluster in the old Viking port towns, Waterford among them. The implication is that St Olave's has Hiberno-Norse origins, predating the Anglo-Norman arrival in the late twelfth century, though the earliest written reference to the church only surfaces in 1407. By 1615 it was already described as a ruin, its nave and chancel both gone to decay. A repair was carried out in 1677, but this proved insufficient, and the church was entirely rebuilt in 1734. Period maps tell a consistent story: both a 1673 map and one produced by Phillips in 1685 show the building as a simple rectangle, modest in form and not especially remarkable to look at from the outside. What makes it interesting is precisely what was retained when the eighteenth-century builders got to work. Rather than clearing the site entirely, they incorporated that surviving stretch of the medieval west wall, doorway and all, into the new structure. The blocked archway now sits sealed within it, neither demolished nor restored, just absorbed.