▁I vy ▁was ▁removed ▁from ▁the ▁keep ▁between ▁ 1 9 1 9 ▁and ▁ 1 9 3 1 ▁and ▁the ▁plant ing ▁in ▁the ▁cast les ▁scale d ▁back . ▁In ▁ 1 9 6 0 ▁the ▁origin ▁of ▁B ole y ▁Hill ▁was ▁investig ated ▁arch ae olog ically , ▁but ▁the ▁exc av ations ▁failed ▁to ▁provide ▁firm ▁d ating ▁evidence . ▁ ▁The ▁castle ' s ▁state ▁was ▁ass essed ▁in ▁ 1 9 6 1 , ▁and ▁the ▁cost ▁of ▁rep airs ▁estimated ▁at ▁£ 3 0 , 0 0 0 ▁( equ ivalent ▁to ▁£ 1 . 1   mill ion ▁in ▁ 2 0 0 9 ▁terms ). ▁The ▁Ministry ▁of ▁Public ▁Building ▁and ▁Works ▁took ▁over ▁care ▁of ▁the ▁castle ▁from ▁the ▁Corporation ▁of ▁Ro chester ▁in ▁ 1 9 6 5 . ▁Records ▁of ▁the ▁Ministry ' s ▁conservation ▁work ▁have ▁gone ▁missing , ▁so ▁precisely ▁what ▁was ▁done ▁is ▁unclear . ▁Between ▁ 1 9 6 2 ▁and ▁ 1 9 6 5 ▁the ▁council ▁removed ▁buildings ▁from ▁the ▁castle ' s ▁d itch . ▁Guard ians hip ▁transferred ▁to ▁English ▁Heritage ▁in ▁ 1 9 8 4 . ▁Since ▁ 1 9 9 5 ▁the ▁City ▁of ▁Ro chester ▁has ▁been ▁responsible ▁for ▁daily ▁management ▁of ▁the ▁castle . ▁Des cal ing ▁at ▁the ▁start ▁of ▁the ▁ 2 1 st   century ▁contributed ▁to ▁the ▁decay ▁of ▁the ▁keep , ▁and ▁one ▁of ▁the ▁m ural ▁to wers ▁was ▁in ▁need