The castle appears on the 1655-9 Down Survey map of Portnashangan parish, positioned near the townland boundary with what was then called Brackcastle, now known as Brockagh. According to the parish terrier from that period, the castle belonged to Richard Tirrell, described as an ‘Irish papist’, and was one of two castles in the area alongside Loughanstown. Curiously, the castle vanishes from all later Ordnance Survey maps, leaving its precise location lost to time.

The story becomes more intriguing with the construction of Ballynagall House in 1808 for James Gibbons. Local tradition suggests this Georgian house incorporated fabric from an earlier structure called Castle Reynell, though the connection between these buildings and the original medieval castle remains unclear. Arthur Reynell, who served as High Sheriff of County Westmeath, had purchased the estate in 1720, lending his name to what may have been either a new house or a renamed version of the old medieval castle.

Today, the ruins of Ballynagall House offer no clear evidence that they occupy the site of the medieval castle. Whether Castle Reynell was a completely new 18th-century construction, a renovation of the medieval structure, or simply a rebranding of Ballynagall Castle itself remains one of those historical puzzles that make Irish archaeology so compelling. What we know for certain is that somewhere in this corner of Westmeath, a castle that weathered centuries of Irish history has vanished almost without trace, leaving only map references and fragments of local memory in its wake.