Saint David's Church (Naas), Main Street North, Naas, Co. Kildare

Look more closely at its north-western end, though, and the disguise slips: a square medieval tower rises through three storeys behind a battlemented parapet, its stonework slate-hung in places, its top floor pierced by a quatrefoil opening and pointed-arch windows that have nothing to do with the eighteenth century at all. This is a house built around a fortification, its irregular, almost accidental plan the result of centuries of adaptation rather than any single architect's design.

The tower itself dates to around 1600, a private defensive structure of the kind once common in Irish market towns, when a family of means needed both a residence and a refuge. By around 1730 it had been absorbed into something grander: an L-shaped range with a projecting bay to the front, a lower wing with a half-dormer attic tucked to the north-east, and a further bay trailing off to the rear, all roofed in slate with cast-iron rainwater goods and rendered chimney stacks. The result reads, from the street, as a conventional gentleman's house of the period, but the tower survives as its structural spine, its rubble-stone walls now roughcast and painted over but still bearing the outline of its original battlements. Inside, timber panelled shutters remain fitted to the window openings, part of the same phase of refinement that gave the house its sash windows in their various patterns, some with as many as eight panes over eight. Only a replacement glazed door, fitted around 1980, disturbs the early character of the front elevation.

The grounds are shared with Saint John's Church, and part of the house's own south-western wall does double duty as a boundary wall to the lane beyond. A detached outbuilding of the same 1730s build stands to the south-east, a double-height structure with an elliptical-headed carriageway running through it, its doors still hung on their original timber frames even though the roof itself was replaced in corrugated iron around 1940. In front of the house, a stretch of stone cobbling from the same eighteenth-century campaign survives underfoot, a small and increasingly rare trace of a paving practice that has otherwise all but disappeared from towns of this size.