Great Castle Head Beacon is one of twin beacons (sea marks) designed by James Douglass, engineer-in-chief of Trinity House. A square stone tower 5.18m (17ft) high and 3.96m (13ft) wide stands an a plinth 0.58m (1ft 11in) high and is toppped by two plain bands of masonary which form a cornice at the summit. The light window faces south-west. Since 1958 a sector light has been shown from a lantern fixed to the roof of the building. In 1970 the light was changed to a sealed beam shown from the roof.

J. Strong, 2003.