The castle is visible from the road and the estate is home to a variety of events including polo. Some 500 acres are now part of a conservation project which, among other things “… provide permissive, open public access to the area around the old castle ruin and provide interpretative material to enable visitors to gain an understanding of the value and importance of the Knepp Castle Estate. “.
Knepp Castle is in the parish of Shipley, on the road from Worthing to Horsham, from which town it is distant 6 miles. The old name is spelt “Knap,” front the Saxon Knoep, the summit of a hill. It was a fortress of the Rapes of Sussex, from very remote times attached to the Honour of Bramber, and built possibly by William de Braose after he had obtained the grant of Bramber, either as a hunting seat—for these Norman lords were mighty hunters, after the pattern of the two first Williams—or as a safe retreat from Bramber. It formed a residence for his descendants for two hundred years after the Conquest, and many of their deeds and grants were signed at Cnap. King John visited this place in April 1206, during a rebellion raised while the kingdom was under interdict by Pope Innocent III., and while he was himself excommunicated for his opposition to the appointment of Langton to the See of Canterbury. He visited it again in 1209 and 1211 and signed some grants “apud Cnap.” The Braoses kept up an immense establishment there of sporting dogs with an official huntsman for hunting deer and wild boar, which were salted for their use and for the King’s in winter.
After restoring Knepp together with Bramber in 1214 to the Braose family, John seized it again, and repaired thither when the confederated Barons were assembled against him in January 1215 at London, and he kept up the hunting arrangements of the Braose family. His queen, Isabella, was there in 1214-15 for eleven days. Just a month before his death, which happened June 19, 1216, John signed an order for this castle to be burnt and destroyed, a warrant possibly not acted on, as we find notices of Knepp and its park as late as 1400. This restless King, in his journeys in Sussex, is said sometimes to have travelled fifty miles in a day, an incredible distance, considering what the roads must have been in those days.
The form of the castle can be traced now from its moat, which was supplied from a branch of the Adur flowing near. It formerly had a shell keep upon the mound, of which traces exist, said to have been destroyed in 1216. The enclosed area was about two acres, and the adjoining meadow, called the “Town-field,” was connected with it by a causeway. The portion of wall still standing is of great thickness, and from the two circular arches observable in a remaining part of the work—the one heading a doorway into the keep, and the other a window over it—the structure would seem to be of early Norman date, though it is not mentioned in the Survey, as indeed very few castles are. (Castles Of England, Sir James D. Mackenzie, 1896)