Camber Castle is one of Henry VIII's Device Forts, also known as Henrician Castles, built to protect the huge Rye anchorage.
Between 1512 and 1514 Sir Edward Guldeford built a circular tower to defend the harbour. This tower was incorporated into a new fort which was built between 1539 and 1544. It was expanded to become a highly symmetrical artillery fort. The original tower was augmented with four outer towers linked by an octagonal wall concealing a covered passage. Part of this construction was directed by Stefan von Haschenperg. Finally, four large D-shaped bastions serving as gun platforms were placed in front of the earlier towers. As the shoreline receded south the height of the central tower was raised in order to maintain the range of the castle's cannon.
However by the end of the 16th century the silting of the Camber made the castle largely obsolete and in 1637 it was disbanded. Read more on Wikipedia
Lowry refers to the castle in a letter to Conrad Aiken dated 5/8/1946; "I hope you and Mary are by now ensconced in Jeakes House, Rye and that the sea-poppies and Camber Castle, not to say tram, and the ships blithely sailing down the meadows are still there, and that that which was once the province of the sea is not now too much a province of the same again by virtue of being a naval base." (Collected Letters Vol 1 Pg. 623). Lowry stayed on many occasions with Aiken in Rye travelling out to Camber a few miles from the town to swim in the sea there. (Gerald Noxon, Miguel Mota, Paul Tiessen On Malcolm Lowry and other writings Pg. 8 and 15). The castle lies several hundred metres from the beach on the edge of Camber.