They had not drifted there by accident. The slabs were found clustered around the foundations of a late medieval bridge, immediately north of the present John's Bridge, and the evidence points to a deliberate act: at some point, gravestones were stripped from a nearby burial ground and packed in as rubble to reinforce the protective apron around the bridge's piers.

The suspected source of the slabs was one of two religious sites close by, either St Mary's parish church, roughly 100 metres to the west, or St John's Priory, about 200 metres to the northeast. One fragment in particular, a limestone slab just over 1.2 metres long and up to 0.58 metres wide, was found actually mortared into the base of a bridge pier. Despite being broken at both the top and the base, it retains a finely incised four-armed cross with fleur-de-lis terminals, the stylised lily-shaped ornaments common to high-status medieval stonework, and a lozenge-shaped opening at the centre of the cross-head. One of the terminals has been broken off. The style places it in the 13th or 14th century, a period when Kilkenny was developing rapidly as an Anglo-Norman urban centre. That a graveslab of this quality ended up as bridge ballast says something quietly unsettling about the priorities, or perhaps the urgencies, of whoever ordered the work.

The recovered slabs are now kept in Magdalen Tower on Maudlin Street in Kilkenny, a surviving remnant of a medieval hospital precinct, which gives them at least a loosely appropriate resting place after their long detour through a river bed.