Just southwest of Westbury, and northwest of Mondaytown (I like that one) this one is quite easy to find, but parking can be rather problematical. Even more so when they were torturing the hedges up and down the road, but I found a spot, took it as my own and nonchalantly walked passed the tractor doing it's hedge thing and proceeded towards the fort.
Passing a sign on the very gate I wanted that read Private no trespassing, bugger. I wasn't going to waste time seeking permission, especially if it wouldn't be given, so I walked out of sight of the tractor, the negative signed gate and the farm and leapt cat like over the fence. I'm in, I whispered to my non real accomplice.
As thesweetcheats link says this fort has been remodeled in the medieval period, in places quite extensively.
The defenses outside the wood are slight at best, still recognisable, but slight. But once in the welcoming shelter of some mature trees the ditches are deep and the banks are high.
Firstly I followed the long impressive ditch south on its northern side, that doesn't sound right, but you have to remember that the fort is positioned southwest to northeast. Half way along the interior of the fort is the Norman motte on top of which is a short section of curving wall, I like castles and older forts, so it was nice to get two for the price of one, which is free. But it was/is difficult to separate the two. South west of the motte is a maze of high banks and ditches, one ditch seems to have gone right through solid rock.
Beyond the maze further south is what I took to be both the original and medieval entrances, some Norman stonework is visible here too. More ditches here as well, I follow one and it takes me to the gate with the Private sign on it, perfect, I jump it gleefully and walk back to the car trying not to look like I just got away with something, I don't think I pulled it off entirely successfully.