But even within that well-documented complex, there are quieter puzzles. Incorporated into the north-east end-wall of St Michael's Church, at the base where a plinth marks the masonry line, is a small section of an earlier structure. It sits there, partly absorbed into the later building, the kind of physical detail easy to miss unless you know to look for it.

The suggestion, recorded by O'Sullivan and Sheehan in 1996, is that this earlier remnant may itself have been a church, predating the St Michael's structure that was eventually built over or against it. What makes this more than speculation is a radiocarbon date obtained by Berger from a mortar sample taken from the earlier fabric. The result, UCLA 2738D, came back as 1250 plus or minus 25 BP, a measurement that calibrates to the mid-ninth century. Radiocarbon dating of mortar, which analyses the lime binder rather than organic inclusions, can carry its own interpretive complications, but the date broadly fits the period of intense monastic activity on the island. If the reading is sound, the fragment may represent an earlier phase of ecclesiastical building on Skellig Michael, a structure already standing when the Viking Age was reshaping monastic life across Ireland and when the community on this rock was developing the stone oratories and beehive cells that survive today.