King John's reputation is of a suspicious vengeful and treacherous ruler. It was his behaviour as monarch that prompted English Barons to rebel and enact the Magna Carta which stripped John of many of his powers. However he was the first King of England since the Norman conquest who could speak English.
He took interest in judicial and financial administration and his reign saw important advances in the exchequer, in methods of taxation and military organisation and in the grant of chartered privileges to towns. This explains why he invested so much in Limerick City, what would have been considered an distant outpost at that time.