Look more carefully, though, and the building begins to contradict itself. The fireplaces at the western end sit at an angle, placed back-to-back on either side of a partition wall in a way that suggests they were not designed for the building as it now stands. According to Oliver Langley, whose family owns the property, the house was originally two storeys higher still, meaning what survives today is a reduced version of something considerably more substantial. And tucked into the eastern gable, a single-light window with external chamfering and a hood-moulding, a carved stone drip course above the opening, sits in masonry that was rebuilt by Langley's grandfather, quietly advertising its own much older origins.

The Civil Survey of 1654 to 1656 recorded at Archerstown 'a stone house, a bawne, a mill in repaire and a castle out of repaire'. A bawn, in Irish architectural terms, is a walled enclosure associated with a fortified house or tower, and the ruined castle the survey mentions is almost certainly the tower house that still stands immediately to the east of the present building. James Archer is listed as proprietor in 1640, lending the townland its name, but the Cromwellian settlement of the 1650s brought the Langley family into possession, and they have remained there since. It is quite possible that the seventeenth-century stone house referred to in the 1654 survey was never entirely demolished but absorbed into the structure that was later given its Georgian exterior. The walls, measured at between 0.73 and 0.8 metres thick, are consistent with earlier construction rather than standard Georgian domestic building.