Ogham is an early medieval script, typically carved along the edges of upright stones, used to record personal names and lineages in a form of Old Irish. But at Greenhill, the stones may be doing double duty as markers, their positions hinting at the arc of a much larger and older structure that has otherwise vanished from view.

In 1985, a limited excavation was carried out at the site to allow for the installation of cattle grids around the two ogham stones. The work was modest in scope, but it produced an intriguing observation. Beneath the present field boundary near the more northerly of the two stones, the excavator noted what was described as an old cut feature, a trace of something deliberately made in the ground at some earlier point. Looking at the broader shape of the field, with its curving eastern and southern boundaries, the excavator proposed that those boundaries might follow the line of a very old enclosure, one that was elongated and oval, measuring roughly 200 metres north to south and 150 metres east to west. The two ogham stones, it turns out, sit on the south-eastern arc of this proposed outline.

Nothing about the enclosure has been confirmed by further excavation, and its date and original purpose remain unknown. What makes the situation quietly compelling is the layering: a field boundary that may be following a curve laid out long before anyone now living could know, and two inscribed stones that might have been placed, deliberately or coincidentally, along that same ancient line.