In this image,can be seen,the now dry moat around the base of the motte.In the middle of the image,the brighter green is the floor of the moat,winding its way around the steeply sloped motte(twixt the brighter green and the branch,and to the lhs of that behind the bush).The motte stands about 10 feet above the floor of the moat.
see http://www.castleuk.net/castle_lists_midlands/166/wymondley.htm
see http://www.british-history.ac.uk/report.aspx?compid=43600
see http://www.hertsdirect.org/libsleisure/heritage1/archaeology/moreaboutarch/archsites/wymondleymotte/
see http://www.castlefacts.info/castledetails/castleDetails3.aspx?uin=11566