▁reached ▁by ▁a ▁stone ▁cause way ▁across ▁a ▁d itch , ▁rather ▁than ▁a ▁draw bridge . ▁A ▁tower ▁containing ▁a ▁post ern ▁gate ▁was ▁located ▁in ▁the ▁north - west ▁corner ▁of ▁the ▁en closure , ▁built ▁at ▁the ▁close ▁of ▁the ▁ 1 4 th   century ▁to ▁guard ▁the ▁bridge ▁over ▁the ▁Med way . ▁The ▁tower ▁and ▁post ern ▁no ▁longer ▁stands , ▁but ▁ 1 9 th - century ▁anti qu ary ▁and ▁engineer ▁G . ▁T . ▁Clark ▁made ▁some ▁notes ▁on ▁the ▁structure ▁while ▁it ▁was ▁still ▁standing ▁and ▁commented ▁that ▁it ▁had ▁mechan isms ▁to ▁lift ▁supplies ▁for ▁the ▁castle ▁from ▁the ▁river . ▁The ▁western ▁part ▁of ▁the ▁stone ▁outer ▁wall , ▁a ▁stretch ▁facing ▁the ▁river , ▁dates ▁from ▁when ▁G und ulf ▁built ▁the ▁first ▁wall ▁en clos ing ▁the ▁castle . ▁In ▁the ▁ 1 9 th   century ▁a ▁re vet ment ▁was ▁added ▁to ▁strength en ▁the ▁decay ing ▁wall . ▁Like ▁the ▁keep , ▁it ▁was ▁constructed ▁using ▁Kent ish ▁R ag stone . ▁This ▁part ▁of ▁G und ulf ' s ▁wall ▁was ▁ ▁thick ▁at ▁the ▁base , ▁narrow ing ▁to ▁ ▁at ▁the ▁top ; ▁it ▁rose ▁to ▁a ▁height ▁of ▁around ▁. ▁Four ▁em bras ures ▁were ▁added ▁to ▁this ▁part ▁of ▁the ▁wall ▁in ▁the ▁ 1 3 th   century ; ▁the ▁build ers ▁im itated ▁Norman ▁design . ▁At ▁the ▁northern ▁end ▁of ▁the ▁ 1 2 th - century ▁stretch