Marconi Blocks, East Lighthouse, Rathlin Island, Ballycastle, Co Antrim, BT54 6RT

Located just outside the lighthouse grounds on Rathlin Island, are three concrete blocks set into the ground. These blocks, likely dating between 1900 and 1919, served as anchor stays for a mast erected by Lloyds of London, the shipping insurers. The mast was associated with a watch house used for observing transatlantic shipping, with wireless communication relayed to Lloyd's London headquarters.

The blocks are positioned in a line: the first is 13 meters south of the gated entrance to the lighthouse grounds, the second 24 meters beyond that, and the third a further 35 meters on. Each block is approximately 60cm by 60cm in plan. Originally, the name "LLOYDS" was cast into their tops, but due to weathering, only "LOY" is now readable on the first block, "LLOYD" on the second, and the inscription is indecipherable on the third.

In 1898, George Kemp and Edward Glanville, assistants to Guglielmo Marconi, demonstrated wireless telegraphy to Lloyds of London officials. A Morse signal was transmitted wirelessly from an aerial strung from the East Light tower and received in Ballycastle. Following this demonstration, Lloyds built a signal station—a watch house and mast—on the plot beside the lighthouse. The blocks are of industrial archaeological interest and their extent of listing comprises the foundation stones of the former tower and mast structure.