Under unwritten constitution, part of which are constitutional conventions courts are unable to guarantee obedience to constitutional rules and values. In United Kingdom it is therefore the monarch who stands as a custodian of the constitution. Royal prerogatives that are normally exercised only on advice of responsible ministers can be used to protect constitution. The most important are so-called reserve powers to dismiss prime minister and other ministers, to dissolve parliament and to give royal assent. The Monarch is able to successfully perform this function despite the want of democratic legitimacy but he should always be cautious and act only if he is perfectly positive that his intervention is absolutely necessary. He would therefore be entitled to intervene only in a dire emergency if political actors stood against the fundamental rules of parliamentary democracy, responsible government and sovereignty of the people.