For years, the residential tower attached to the north side of St Mary’s Church was mistakenly identified as the medieval stronghold, but recent research has revealed a far more intriguing story. The actual castle’s location remained elusive until local archaeologist Helen Farrell uncovered crucial evidence in the De Vesci Papers at the National Library of Ireland. A 1699 map of Lucan village clearly shows a tower house annotated as ‘The Castle’, positioned north of a medieval road and east of both Lucan Church and Lucan House.

Today, a peculiar building called ‘Ard Garon’ on Dispensary Lane stands where this medieval castle once dominated the landscape. The National Inventory of Architectural Heritage describes it as an unusual semi-detached structure dating from around 1830, but its odd appearance hints at something much older beneath the Victorian modifications. The building’s unusual facade suggests it incorporates a two-storey medieval tower that was extended and altered in the 19th century, creating the distinctive appearance that puzzles visitors today. This theory gains weight when considering that the site perfectly matches the location shown on the 1699 map.

The question of whether Lucan had one or two medieval castles remains tantalisingly unresolved. Some historians, including Mike Salter, have suggested that a castle stood beside the present 18th-century Lucan House, possibly built by Sir William Sarsfield after he acquired the estate in 1534 following the Earl of Kildare’s attainder. This castle later passed through the hands of Cromwellian Sir Theophilus Jones before being restored to Patrick Sarsfield, who became Earl of Lucan. If both sites held castles, ‘Ard Garon’ might represent the original manorial castle, whilst the one near Lucan House could have been a later addition to the manor’s defences.