Prorogation is a political process in which the Parliament of the United Kingdom is suspended after the closure of one parliamentary session until a State Opening of Parliament several days later. The suspension of Parliament has the effect of ending all parliamentary proceedings and any proposed legislation which does not pass prior to prorogation must be re-introduced in the next session of Parliament. Although typically a routine process, there have been several historical cases where prorogation has been controversial; most notably, the English Civil War was triggered amidst tensions between Charles I, who would only convene Parliament to pass controversial ship taxes, and Parliament, who sought more powers to scrutinise the King, going so far as to pass laws which prevented its own prorogation or dissolution. Eventually, Parliament went to war with and subsequently executed Charles I for the crime of tyranny; his successor as head of state, Oliver Cromwell, also had tensions with Parliament and eventually purged and expelled the "Long Parliament" in favour of another.