Built in 1898-9, South Boom Battery was built to protect the southern end of a defensive boom which was to be placed across the Medway in times of war. The battery was constructed on the north-eastern tip of Burntwick Island, enclosed on its south western side by a water-filled ditch. At the end of each ditch was a double machine-gun position. Only the eastern emplacement remains intact. The battery was also equiped with two pairs of 12 pdr QF (quick firing) guns on the northern edge of the island of which on their concrete pads remain. Also there are the traces of three DEL (defence electric lights) and the anchor point for the boom. All are being slowly destroyed by tidal action. Other surviving features included a brick chimney, a yellow brick barracks building and a metal-framed structure.