Practices relating to the exercise of their functions by the Crown, the government, Parliament, and the judiciary that are not legally enforceable but are commonly followed as if they were. One of the most important is that the Crown must exercise its constitutional powers only in accordance with the advice of ministers who collectively command the support of a majority of the House of Commons. There is no single reason why conventions are observed. For example, it is a very old convention that Parliament must be summoned at least once a year. If that were not to happen, there would be no annual Finance Act and the government would be able to function only by raising illegal taxation. By contrast, if the Crown broke the convention that the royal assent must not be refused to a Bill duly passed by Parliament, illegal conduct would not necessarily follow (although the future of the monarchy could well be at risk). The basic reason for obeying conventions is to ensure that the machinery of government should function smoothly; conventions have not been codified into law and therefore can be modified informally to meet changing circumstances. Case: AG v Jonathan Cape Ltd  QB 752 (Spycatcher case).