east ▁England ▁in ▁prepar ation ▁for ▁a ▁possible ▁invasion . ▁Among st ▁these ▁was ▁Ro chester ▁and ▁in ▁ 1 2 0 6 ▁John ▁spent ▁£ 1 1 5 ▁on ▁the ▁castle ' s ▁d itch es , ▁keep , ▁and ▁other ▁structures . ▁Under ▁England ' s ▁An ge vin ▁k ings ▁royal ▁cast les ▁in ▁south - east ▁England ▁were ▁inv ested ▁in ▁to ▁protect ▁the ▁country ▁from ▁invasion ; ▁Ro chester ▁was ▁one ▁of ▁the ▁most ▁important . ▁ ▁King ▁John ▁C ust ody ▁of ▁Ro chester ▁Castle ▁remained ▁with ▁the ▁Arch b ish ops ▁of ▁Can ter bury ▁until ▁the ▁end ▁of ▁the ▁ 1 2 th ▁century . ▁Despite ▁asc ending ▁to ▁the ▁throne ▁in ▁ 1 1 9 9 ▁King ▁John ▁did ▁not ▁confirm ▁Hub ert ▁Walter ▁as ▁the ▁castle ' s ▁cust od ian ▁until ▁July ▁ 1 2 0 2 . ▁John ▁may ▁have ▁wished ▁to ▁reg ain ▁direct ▁control ▁of ▁what ▁was ▁an ▁important ▁castle . ▁The ▁crisis ▁of ▁John ' s ▁rule ▁began ▁in ▁ 1 2 1 2 ▁with ▁the ▁discovery ▁of ▁a ▁plot ▁to ▁over throw ▁him . ▁De fe at ▁at ▁the ▁Battle ▁of ▁B ouv ines ▁in ▁July ▁ 1 2 1 4 ▁marked ▁the ▁end ▁of ▁John ' s ▁amb itions ▁to ▁re take ▁Norm andy ▁and ▁ex ac erb ated ▁the ▁situation ▁in ▁England . ▁He ▁returned ▁to ▁England ▁in ▁October ▁and ▁a ▁few ▁months ▁later ▁bar ons ▁in ▁the ▁north ▁of ▁England ▁were ▁act ively ▁challeng