The 1657 Down Survey map shows two ruinous medieval castles on this site, which belonged to Thomas FitzSymons, an Irish Catholic landowner who lost his estates during the Cromwellian confiscations. When Henry Pakenham acquired these forfeited lands in the latter half of the 17th century, he built a square fortified house, possibly incorporating or replacing the medieval structures. This plantation house, constructed around 1655, forms the hidden core of what would become Tullynally Castle, though any obvious traces of these earliest features have long since vanished beneath subsequent renovations.

The Pakenham family transformed their relatively modest stronghold into something far grander over the following centuries. A 1736 family diary reveals formal gardens stretching south from the house, complete with ornamental canals, basins and tree lined avenues; a baroque landscape that Thomas Pakenham swept away after 1740 in favour of the fashionable ‘natural romantic’ style. The house itself underwent its most dramatic metamorphosis between 1800 and 1850, when successive Gothic Revival and Tudoresque renovations added towers, bartizans and crenellated parapets to every corner. What began as a two storey structure around 1730 gained a third floor by 1780, whilst extensive wings containing kitchens, stables, laundry and staff quarters sprawled around two courtyards to the north.

Today’s Tullynally Castle presents an irregular, almost fantastical silhouette; a five bay, three storey country house dressed in ashlar limestone and Gothic fancy, with projecting end bays and a complex accumulation of additions that speak to nearly four centuries of continuous occupation by the Pakenham family. Whilst the National Inventory of Architectural Heritage suggests the original fortified house may still lurk somewhere within the existing edifice, the layers of roughcast render, exposed limestone and Victorian romanticism have thoroughly obscured any definitive evidence of Henry Pakenham’s square plantation castle or the medieval ruins that preceded it.