by constitutional convention, an MP. The prime minister is appointed by the monarch and their appointment is governed by constitutional conventions. However, they are normally the leader of the political party with the most seats in the House of Commons and hold office by virtue of their ability to command the confidence of the House of Commons. The prime minister not only has statutory functions (alongside other ministers), but is the monarch's principal adviser and it is for them to advise the monarch on the exercise of the royal prerogative in relation to government. In particular, the prime minister recommends the appointment of ministers and chairs the Cabinet. Administrative divisions The geographical division of the United Kingdom into counties or shires began in England and Scotland in the early Middle Ages, and was completed throughout Great Britain and Ireland by the early Modern Period. Administrative arrangements were developed separately in each country of the United Kingdom, with origins that often predated the formation of the United Kingdom. Modern local government by elected councils, partly based on the ancient counties, was established by separate Acts of Parliament: in England and Wales in 1888, Scotland in 1889 and Ireland in 1898, meaning there is no consistent system of administrative or geographic demarcation across the UK. Until the 19th century there was little change to those arrangements, but there has since been a constant evolution of role and function. The organisation of local government in England is complex, with the distribution of functions varying according to local arrangements. The upper-tier subdivisions of England are the nine regions, now used primarily for statistical purposes. One of the regions, Greater London, has had a directly elected assembly and mayor since 2000 following popular support for the proposal in a 1998 referendum. It was intended that other regions would also be given their own elected regional assemblies, but a proposed assembly in the North East region was rejected by a referendum in 2004. Since 2011, ten combined authorities have been established in England. Eight of these have elected mayors, elections for which first took place in May 2017. Below the regional tier, some parts of England have county councils and district councils, and others have unitary authorities, while London consists of 32 London boroughs and the City of London. Councillors are elected by the first-past-the-post system in single-member wards or by the multi-member plurality system in