The purpose of this paper is to present a re-evaluation of the reign of England\u27s King John (1199-1216) from a fiscal perspective. The paper seeks to explain John\u27s innovations in terms of widening the scope and severity of tax assessment and revenue collection. In particular, the paper seeks to highlight the significance of Hubert Walter as the king\u27s financial adviser. He exercised a moderating influence in the first half of John\u27s reign and was the guiding hand in the successful introduction of innovative measures designed to increase revenues. These became extreme after his death in 1205, when John lacked his counsel. It is further suggested that the Magna Carta was a direct reaction to such financial severity. Many of the clauses in Magna Carta refer specifically to John\u27s tax innovations and severity. Linked to this, the paper argues that these events were critical to the establishment of the principle of taxation by consent. As a result of the innovative and extreme nature of John\u27s fiscal measures, it is our contention that John is a significant influence in moving away from deep-rooted feudal systems to the beginnings of what we would now understand as a national taxation system. This occurred against the background of a period of transition in state finance from a domain-based to a tax-based state