Excavation of the site in 1929 by S.E. Winbolt indicated that it dated to the 1st Century AD and may have been constructed by Belgic tribes of Celts who were settling this part of Britain in the period prior to the Roman invasion of Britain. The hillfort was defended by double ramparts to the west and north with escarpments on the eastern and southern slopes. The outer ditches were originally about three metres deep and six metres wide. The inner ditches were considerably larger, some four metres deep and nine metres wide.
At 856 feet (261 m) Holmbury Hill is the fourth highest point in the county. It is 2 miles (3.2 km) west of Leith Hill, the highest point in Surrey at 965 feet, separated by a deep ravine draining north and south. The major hills of Surrey do not form one ridge. The third highest point in the county, unlike all of the other highest six which are in the Greensand Ridge is along the North Downs, the other main range of hills in Surrey, to the north, in Woldingham civil parish at Botley Hill. Together these ranges of hills contribute to the Surrey HillsArea of Outstanding Natural Beauty.