drops by local authorities. An archaeological study in the 21st century identified further potential promontory fort presence. In October 2018, the Gaisford-St.Lawrence family, heirs to the Lords of Howth, agreed to sell Howth Castle and demesne, including Ireland's Eye, to the Tetrarch investment group, as part of a multi-million euro deal, and on the 28 May 2019, for the first time in centuries, the freehold of the island passed outside the family. Tetrarch confirmed that the island would remain open to visitors, and stated their commitment to maintaining its beauty and accessibility. Buildings The ruins of an 8th-century church (the Church of the Three Sons of Nessan) and a Martello tower are the only signs of previous habitation. Cill Mac Nessan In 1837 the remains of the church of the sons of Nessan were prominent on the south west side of the island. The church is often, though inaccurately, known as St Nessan's Church. It functioned as parish church for Howth until 1235, being replaced by the church of St Mary's Abbey, and later a church in the village, perhaps partly due to the limitations of having to take a boat for every service. A burial ground exists beside the church. No evidence of a broader settlement, such as a full monastery, has been found to date but scholars have noted that were secondary buildings made of wattle-and-daub, for example, traces might not have survived. The ruins of a church which probably began as a simple single-chamber chapel but which later took on a nave-and-chancel form, were subject to attempted restoration in the 19th century. When studied by Robert Cochrane, they were measured at around by –, with walls nearly in thickness. The round tower on the roof had a circumference of , and Petrie computed its likely full height at . Stones were removed, notably from the doorway area of the church, before 1845, to be used in the building of a new parish church in Howth village. Martello tower The Martello tower, built in 1803 or 1804, was one of three constructed in the Howth area, and 26 in northern County Dublin, on the instructions of Prince Frederick, Duke of York and Albany to repel a possible invasion by Napoleon. Hosting two 24-pound guns, it was one of the larger Martello towers. It was constructed on a rocky area in the northwestern corner of the island, allowing it