Here's an interesting question (or perhaps it isn't) Where was Ireland's first lighthouse?
Well, according to tradition, St. Dubhan, a Welsh monk, and contemporary of the much more famous Patrick, came to this lonely peninsula and established a monastery here in 452ad (about tea-time, as Monty Python would say) Here he established a lighted beacon for ships to warn them of the treacherous coastline hereabouts, a beacon that was tended for 700 years until the Tower was built in the early 13th Century.
But where was it, this beacon? It was probably a chauffer on top of a mound of stones. Adjoining Hook Lighthouse itself is an old wall and a small plaque on a wall saying 'Site of Monks' Chapel' To my eyes the wall in the top picture looks younger than 5th century but I'm no expert. If they had the chauffer right on the point, then it would probably have been around the site of the present tower.
Of course, they could have had it about a mile further north, where the ruins of the original monastery still stand, surrounded by a small graveyard. To be honest, I wouldn't build a monastery and then have to maintain a beacon a mile away but hey, those ancient monks were quare fellers altogether.
Anyhow, to cut to the chase, Ireland's first lighthouse lay between the ruins of the monastery and the tip of Hook Point. Can't narrow it down further than that, unless anybody else has further information.