 Henry's successor, Richard I, paid relatively little attention to Kenilworth, but under King John significant building resumed at the castle. When John was excommunicated in 1208, he embarked on a programme of rebuilding and enhancing several major royal castles. These included Corfe, Odiham, Dover, Scarborough as well as Kenilworth. John spent £ 1,115 on Kenilworth Castle between 1210 and 1216, building the outer bailey wall in stone and improving the other defences, including creating Mortimer's and Lunn's Towers. He also significantly improved the castle's water defences by damming the Finham and Inchford Brooks, creating the Great Mere. The result was to turn Kenilworth into one of the largest English castles of the time, with one of the largest artificial lake defences in England. John was forced to cede the castle to the baronial opposition as part of the guarantee of the Magna Carta, before it reverted to royal control early in the reign of his son, Henry III.
