The low hill that once commanded wide views in every direction, and that was known as Telegraph Hill on maps drawn around 1908 to 1909, has been swallowed by the sea. The sandy headland here is an actively eroding one, and whatever structure stood on its summit has long since gone with it. Even before the erosion completed its work, remarkably little was recorded: no precise location, no clear description of the original form, just a name on a map and a handful of documentary references pointing to something that once mattered a great deal.

What stood here was part of one of the more ambitious early-warning systems of the Napoleonic era. The British Board of Ordnance constructed a chain of over eighty signal stations around the Irish coast in the early nineteenth century, running continuously from Malin Head in Donegal south and around to Dublin Bay, with the specific purpose of detecting and relaying news of any approaching French invasion fleet. Signalling between stations was carried out using naval signal posts, allowing information to travel rapidly along the chain. According to the historian Paul Kerrigan, the station at Blackwater Head was likely completed by October 1804, with the signal mast erected around the same time. The nearest stations in the chain were at Fort Point near Rosslare, roughly eleven kilometres to the south-southwest, and at Cahore Point, about sixteen and a half kilometres to the north-northeast. Both of those have also since been lost, one to erosion, the other demolished. The whole system was wound down by the mid-1810s, once the threat of French invasion had receded. By the time the Ordnance Survey mapped the area in 1839 to 1840, the site was shown as a coastguard station with a telegraph still indicated there, suggesting the signal infrastructure may have been absorbed into the later coastguard operation, as happened at several sites in West Cork. A low hill, a mast, a few decades of watchfulness, and then the slow work of the sea.