The main part of the castle was built in the early seventeenth century- 1614 is the date on the O Reilly coat of arms over the front door although this be inaccurate by a few decades.
The newer wing at Ballinlough was added by Sir Hugh O Reilly in about 1790 and is probably attributable to the amateur Thomas Wogan Browne, also responsible for Malahide Castle, the home of Sir Hugh O Reilly s sister, Margaret. The ground floor contains a large drawing room and dining room with four first-floor bedrooms approached by a vaulted corridor above. The spacious interiors have what may be the tallest windows in a private house of this period, overlooking the woods and lake. The chimneypiece in the drawing room is identical to a Wyatt chimneypiece at Curraghmore, Co. Waterford.
"The Nugents at Ballinlough (who are really O’Reillys, having assumed the surname of Nugent in 1812 to inherit a legacy) are almost unique in being a Catholic Celtic-Irish family who still live in their ancient castle; for the other Celtic-Irish families who have remained Catholic and kept their ancestral homes have almost all abandoned their castles in favour of houses built at a later period. At Ballinlough the old castle was never abandoned but re-constructed in the 1730s so that it assumed the appearance of a pleasant 2 storey 7 bay house of the period, with narrow windows, a breakfront centre and a segmental-pedimented doorcase; originally it had a high pitched roof but was re-roofed at a later date, probably circa 1780 when the breakfront was raised a storey to form a tower like central attic which was battlemented, like the rest of the roof line, to make it in keeping with the higher 2 storey castellated range which was added at this period at right angles to the original front by Hugh O’Reilly (afterwards 1st Bt) who eventually assumed the surname of Nugent. The new range which has two slender round corner towers, is rather similar to one side of Malahide Castle, Co. Dublin, the home of Hugh O’Reilly’s brother-in-law, which was re-built about 10 years earlier; so that it seems likely that the work at Ballinlough and Malahide was by the same architect or builder; Dr Rowan suggests that it might be the amateur architect Thomas Wogan Browne, of Castle Browne who himself was connected to both families. The delicate Gothic plasterwork in the drawing room and dining room incorporates some neo-Classical elements; and the drawing room chimney piece is identical to one known to be by Wyatt at Curraghmore, Co. Waterford. The other notable interior is the hall in the earlier part of the castle and dating, in its present form, from circa 1750. It rises through 2 stories and is spanned by a bridge-gallery, behind which is the staircase; a very unusual arrangement for its period, although one of which there is another example only a couple of miles away across the Meath border at Drewstown. The decoration of the hall at Ballinlough is of a much higher quality than that of the Drewstown hall; there are panels of fruit and flowers in plasterwork on the walls, a cornice in the same style and a richly carved frieze of acanthus below the gallery balustrade; which, like that of the staircase has slender wooden balusters."
Burke’s Guide to Country Houses – Volume 1 - Ireland
1978 Mark Bence-Jones
"All that anyone might hope for in an Irish country house is present at Ballinlough Castle. A wooded landscape setting, a charming and eccentric house of several building periods and a family history of distinction. It is a tribute both to the capabilities of the C18 gentleman-architect and to the tenacity of the Catholic O’Reilly family, who remained in ownership of Ballinlough from the later Middle Ages. Having accepted a baronetcy in the late C18, Sir Hugh O’Reilly changed the family name to Nugent in 1812. During the C19 the pursuit of military careers in the Austrian army (as was common among the Irish Catholic ascendancy) caused a hiatus in the family’s occupation of the estate. It was only in 1927, after the lands had been disposed of by the Land Commission and the house earmarked for demolition, that Sir Hugh Nugent returned to Ballinlough, recovered the castle and began the work of restoration.
Today the house is among the most elegant in North Leinster."
"At first glance it might be thought that the Nugents of Ballinlough belong to the "Old English" group of Irish country house owners, of whom only a handful survive. yet closer investigation of the family history reveals something much more remarkable, indeed the very rare distinction of being a Catholic Celtic-Irish family still seated in the ancestral castle."
Great Houses of Ireland, Hugh Montgomery-Massingberd 1999
"The castle and demesne of Ballinlough had an appearance of antiquity highly gratifying to my feelings...I reined in my horse within a few perches of the grand gate of Ballinlough to take a view of the castle: it stands on a little eminence above a lake which beautifies the demesne; and not only the structure of the castle, but the appearance of the trees, and even the dusky colour of the gate and walls, as you enter, contribute to give the whole scenery an appearance of antiquity, while the prospect is calculated to infuse into the heart of the beholder, a mixed sentiment of veneration and delight"
Atkinson's The Irish Tourist (1815)