 Construction progressed at a rate of about 10 feet ( 3 @.@ 0 m ) per year . It was probably finished before Corbeil died in 1138 and definitely before 1141 , when Robert , Earl of Gloucester , was imprisoned there during the Anarchy of King Stephen 's reign . It is likely that after the keep was built there was no further building activity in the 12th century , although the structure was maintained . Though held by the Archbishops of Canterbury under the king , the monarch was still responsible for financially supporting the castle . Continuous records of royal expenditures known as " Pipe Rolls " began in the reign of Henry II , and included in the rolls are details of expenditure on Rochester Castle 's upkeep . During the 12th century , these were generally small figures , but in 1172 – 1173 more than £ 100 was spent on the castle , coinciding with the rebellion of Henry II 's sons . Following the fall of Normandy in 1204 to the French forces of King Philip II , King John increased his expenditure on the castles in south @-@ east England in preparation for a possible invasion . Amongst these was Rochester and in 1206 John spent £ 115 on the castle 's ditches , keep , and other structures . Under England 's Angevin kings royal castles in south @-@ east England were invested in to protect the country from invasion ; Rochester was one of the most important . 
