It is bonded into the wall as a lintel, holding up the structure above the steps, but look at its face and you find a graveslab that never quite became one, pressed into an entirely different kind of service before it was ever finished.

The slab measures 1.1 metres long and 0.55 metres wide, and its origins are dated to the 13th or 14th century. Incised across its surface is a cross that was never completed: the shaft is plain and clear, but the cross head was barely begun, reduced to the most rudimentary of gestures before work stopped. What makes the stone stranger still is what was scored over it afterwards. At its centre, cutting directly across the shaft of the unfinished cross, is an almost perfectly circular three-strand spiral, and to its right are six intersecting circles. These are not decorative flourishes intended for the finished graveslab; they are almost certainly mason's working drawings, the kind of geometric trial pieces a craftsman would scratch out when planning proportions or testing compass work for other carvings entirely. The slab, it seems, passed through at least two lives before it reached the tower house: first as an abandoned funerary commission, then as a mason's layout block. When the tower house was built in the 15th or 16th century, the stone was taken up again and set into the staircase as a lintel, a role it still occupies today. Because it is bonded into the walls at both ends, the top and bottom of the slab remain hidden, so whether the cross or the other marks extended further in either direction simply cannot be known.