Built by the Cruise family (variously spelled Crues or Cruwys), who originated from Cruwys Morchard in Devonshire, the castle formed the centrepiece of a medieval manor that once controlled this important crossing point. The castle’s cliff-edge setting, now obscured by trees, was captured beautifully in an 1820 engraving by John Greig, which shows the rectangular tower with its tall chimney stacks rising from both the north and south walls, and the remains of an adjoining hall building.

The Cruise family’s connection to Naul began in 1185 when Stephen de Crues held the manor, though he briefly lost possession before paying King John 15 marks sterling in 1200 to regain his lands. By 1292, when Robert de Cruys died, an inquisition revealed that the castle buildings, constructed with stone walls and oaken timber, had fallen into disrepair and were “altogether unroofed through bad keeping”. The estate then comprised extensive lands including 140 acres in the carrot field, 120 acres in the mill plain, meadows, mountain pastures, and even a sheep pasture called la Roche. The manor maintained its importance through the centuries; by 1641, Christopher Cruise still owned 250 acres here, complete with the old castle, a hall covered with straw, an orchard, garden plots, ten tenements, and notably, an open stone quarry and a decorative grove of ash trees.

Archaeological evidence and historical drawings reveal fascinating details about the castle’s evolution. The original 13th-century structure featured a first-floor entrance accessed by external stone stairs, typical of early medieval fortifications where the main hall occupied the upper level for defensive purposes. Later additions included a ground-floor hall attached to the north side of the tower, whose steeply pitched roof cut across earlier window openings, suggesting continuous adaptation over the centuries. The castle formed part of a larger complex including a possible bawn wall, and sat within a landscape rich with medieval features: a holy well 155 metres to the east, the parish church and graveyard just 80 metres south, a watermill 200 metres west, and a bridge crossing the Delvin River to the northwest. This concentration of medieval structures around the Glen of the Naul created what was described in the early 19th century as a picturesque scene, with the castle keep on its rocky precipice, the church nearby, and Naul Park with its large corn mill on the opposite side of the glen, the mill dam sustained by a natural ledge of rock.