ed ▁at ▁a ▁rate ▁of ▁about ▁ ▁per ▁year . ▁It ▁was ▁probably ▁finished ▁before ▁Cor be il ▁died ▁in ▁ 1 1 3 8 ▁and ▁definitely ▁before ▁ 1 1 4 1 , ▁when ▁Robert , ▁Earl ▁of ▁Gl ouc ester , ▁was ▁imprison ed ▁there ▁during ▁the ▁An archy ▁of ▁King ▁Stephen ' s ▁reign . ▁It ▁is ▁likely ▁that ▁after ▁the ▁keep ▁was ▁built ▁there ▁was ▁no ▁further ▁building ▁activity ▁in ▁the ▁ 1 2 th   century , ▁only ▁maintenance . ▁The ▁castle ▁was ▁held ▁by ▁the ▁Arch b ish ops ▁of ▁Can ter bury ▁under ▁the ▁king , ▁but ▁the ▁monarch ▁was ▁still ▁responsible ▁for ▁finan cially ▁supporting ▁it . ▁Cont inu ous ▁records ▁of ▁royal ▁exp end it ures ▁known ▁as ▁" Pi pe ▁Roll s " ▁began ▁in ▁the ▁reign ▁of ▁Henry   II , ▁and ▁included ▁in ▁the ▁roll s ▁are ▁details ▁of ▁exp end iture ▁on ▁Ro chester ▁Castle ' s ▁up keep . ▁During ▁the ▁ 1 2 th   century , ▁these ▁were ▁generally ▁small ▁figures , ▁but ▁in ▁ 1 1 7 2 – 1 1 7 3 ▁more ▁than ▁£ 1 0 0 ▁was ▁spent ▁on ▁the ▁castle , ▁coinc iding ▁with ▁the ▁re bell ion ▁of ▁Henry   II ' s ▁sons . ▁Following ▁the ▁fall ▁of ▁Norm andy ▁in ▁ 1 2 0 4 ▁to ▁the ▁French ▁forces ▁of ▁King ▁Philip   II , ▁King ▁John ▁increased ▁his ▁exp end iture ▁on ▁the ▁cast les ▁in ▁south -