This is one of the largest and most complex Iron Age hillforts in Europe, and certainly the largest in Britain. Comprising multiple ramparts, the area inside would have protected several hundred people. Subsequent excavations produced an extensive cemetery, revealing evidence of death during battle. This was thought to be during attack at the time of the Roman invasion, and the remains of a Roman temple bears out the fact that the invaders had clearly gained access and taken control of the site.
The earliest evidence of activity consisted of a Neolithic causeway enclosure and bank barrow. During the Bronze age, around 1800 BC, it was an agricultural site. The castle itself (Old English for camp or encampment) was built around 600 BC, and was pretty much like any other hill fort in Britain, until circa 450 BC when major expansion occurred. The enclosed area was almost tripled in size, and the defences made more complex with additional ramparts and ditches.
The remains of the Roman temple (below).
My favourite photo of the day, below, was taken when walking back around the perimeter towards the setting sun in the west.
More photos can be seen in the Photo Gallery album along with these.