A raised mound and ditch,being the earthworks remains of a siege castle of Arundel,dating probably to C1102AD.
It's on private land.This was the best shot I could get.Insignificant as this ditch and mound seem,it,Lyminster siege castle,Ford siege castle,Burpham siege castle and doubtless others yet to be identified are all mentioned in the Anglo-Saxon Chronicles."C1102AD King Henry then beset the castle at Arundel;and when he saw that it could not easily be taken,made his men to build castles before it and then filled them with his men."
see http://www.ecastles.co.uk/philipdavis/English%20sites/3600.html