The current 19th-century house, designed by Robertson, conceals remnants of a much older structure that dates back to the early 17th century. According to historical maps from the Down Survey of 1655-6, the site was marked as both a castle and a large house, suggesting its importance as a significant dwelling in the area.

Local tradition and historical accounts attribute the original building to George Bagenal, who died in 1625. The Bagenal family maintained that parts of this early house were incorporated into what they called “the far end of the long low range” at the rear of the present manor. This oral history, passed down through generations at Dunleckny, kept the memory of the older structure alive even as it disappeared behind later additions and renovations.

The truth of these family stories was dramatically confirmed during refurbishment work in the 1980s. As builders worked on the Victorian manor, they uncovered architectural elements from the earlier building, proving that the old castle wasn’t entirely demolished but rather absorbed into the newer construction. This discovery offers a tangible link to County Carlow’s past, where the pragmatic reuse of older structures was common practice amongst the landed gentry, who often preferred to build upon existing foundations rather than start anew.