A mill on Halnaker hill was noted as present in 1301 in the will of Robert de St John.

A prominent landmark set 128m high on an outlier of the South Downs, it is a prominent landmark. Built in 1740 it was a tower-mill with hand wheel winding by pulling on an endless chain hanging down at ground level. The last milling family was that of Watkins who lived in the mill house close by from 1868 until 1905 when lightning split the main shaft carrying the sweeps and rendered the mill unusable. No repairs were made and the mill became derelict.

In 1934 a major restoration of the outside was carried out by Neves of Heathfield as a memorial to the wife of Sir William Bird, the owner of Eartham House. The damaged wooden wind-shaft was removed and an iron one, specially extended to fit, was put in from Punnett’s Town wind saw mill near Heathfield. New sweeps were also fitted, replaced in 1956 and again in 1994. The empty brick tower had its windows filled in and a new 16-sided beehive cap put on. The working mill was four floors high, Halnaker not needing the usual fifth level as there was so much wind available. It is brick built, now covered with burnt Sussex tiles.

From ‘Boxgrove: History of a Sussex Village’ 2000. The Boxgrove History Group

There is an excellent trail which passes the windmill - Trail leaflet