(1) Palmerstonian coastal fortification began around 1866 now almost vanished. The fort was of triangular form and mounted four guns. The battery on the S. face of the headland functioned in conjunction with two of the four batteries on Flat Holm 4.5km to the S.E., namely Farmhouse Battery and Castle Rock Battery.
RCAHMW AP955145/53-4

(2) Monument comprises the remains of a World War II heavy anti-aircraft gun battery. An irregular area measuring 80m from NE to SW by 55m transversely, consisting of two octagonal concrete gun emplacements incoprporating six ready lockers for ammunition. Between the two gun pits is a rectangular concrete, five-bay magazine for the longer term storage of ammunition, partly buried and surrounded by a blast wall for further protection. There are also two, less robust, gun pits on the Eastern side with some evidence of ammunition lockers in brick and concrete. In the centre of this arrangement lies the concrete command post. The area covered by the original designation did not relate accurately to the remains described in the original scheduling description.

Source: Cadw Revised Scheduling description. FF 22/06/2004