The prime minister is the official head of the government or the senior most minister of the cabinet in the government in a parliamentary system. In several countries which have the parliamentary form of government, the prime minister is the actual head of the government and head of the executive branch of the government; in such countries, the president holds a largely ceremonial position. The office of the prime minister was primarily developed in Britain during the 18th century. The prime minister system in many Commonwealth countries was based upon the British model. Often the prime minister is a member of the parliament and one of his duties is to ensure the passage of bills through the legislature. In many countries like the U.K and India, the prime minister, being the head of the government also takes up other roles or titles in the government. The role of prime ministers is encountered in parliamentary republics like India, France, Germany and Ireland and also in constitutional monarchies like Belgium, Norway,