Rhiannon writes "An Iron Age promontory fort which later became a Norman motte and bailey castle".
Well one things for sure, this site has been re-used for many purposes over many time periods.
Right now it's part of the Manor House Hotel & Golf Club. Their web site proudly boasts
"The history of the grounds of Manor House date back to the Doomsday Book, second only to Stonehenge in terms of archaeological significance in Wiltshire." http://www.manorhousegolf.co.uk/EXCLUSIVE_HOTELS/the_club/history.aspx
I remember visiting this site back in 1985, prior to it being re-landscaped into the golf course. It lies very close to Lugbury long barrow and the Roman Fosse Way. It was very overgrown and difficult to work out. In size the area of the hillfort/castle is comparable with Oliver's Castle on Roundway Hill but the trees and undergrowth camouflage it very well. It felt and looked ancient and the By Brooke, with it's stepping stones and medieval looking bridge gave it an atmosphere of long lost England.
Maybe that's why it was chosen as a film set for Robin Hood (the 80's TV version) for a mock village had been created on the opposite bank of the By Brooke. Scenes from the 1967 film Dr.Dolittle were also shot in and around Castle Combe.
When I visited it in July 08, I came in via the foot path from Nettleton Mill, which is now path of the Macmillan Way. Most of the golfers had retired to the club house for their G+T's and I was able to get onto the private track which runs along side and up the hill of the monument. The remaining area which is most likely to be Iron Age is still covered in dense overgrowth and difficult to explore. I have posted some of the pictures taken that day but it is hard to gauge what are ancient mounds and the modern landscaped bunkers of the golf course.
The site has never been properly excavated although there have been several "investigations" made at various points by Chippenham College under the supervision of Ron Wilcox. Various pillow mounds are present both behind the monument and within what was the Italianate garden of Castle Combe park. Again sketchy notes based upon OS field visits which list "Possible round barrow or ornamental feature". Mesolithic tools have been found to the East, along with Neolithic scrapers and axe heads during excavations at the Shrine of Apollo at Nettleton Shrub (SMR Number ST87NW302). Finds from the area itself include iron arrowheads, spurs, buckle heads and the odd coin or two. A circular stone wall deep underneath the North Western corner of the driving range was detected and Romano-British pottery fragments which were uncovered near the Clubhouse.
An interesting site to explore, if for nothing more than a walk in a beautiful landscape.
Bear in mind that the monument is on a private section of the golf course though and those low flying golf balls can kill.
Although this was later to become a Norman motte and bailey castle, it is thought (according to the smr record on Magic) that the site was originally that of an Iron Age promontory fort, suggested by the fact that immediately below it on the west side is the By Brook, a tributary of the Avon. There's also an extra bank on the NE corner, which also points to a prehistoric origin.