Britain, and in 1801, the Kingdom of Ireland joined to create the United Kingdom of Great Britain and Ireland. The British monarch was the nominal head of the vast British Empire, which covered a quarter of the world's land area at its greatest extent in 1921. The Balfour Declaration of 1926 recognised the evolution of the Dominions of the Empire into separate, self-governing countries within a Commonwealth of Nations. In the years after the Second World War, the vast majority of British colonies and territories became independent, effectively bringing the Empire to an end. George VI and his successors, Elizabeth II and Charles III, adopted the title Head of the Commonwealth as a symbol of the free association of its independent member states. The United Kingdom and fourteen other independent sovereign states that share the same person as their monarch are called Commonwealth realms. Although the monarch is shared, each country is sovereign and independent of the others, and the monarch has a different, specific, and official national title and style for each realm. Although the term is rarely used today, the fifteen Commonwealth realms are in personal union. Constitutional role In the uncodified Constitution of the United Kingdom, the monarch (exclusively referred to in legislation as "the Sovereign", and styled His or Her Majesty) is the head of state. The monarch's image is used to signify British sovereignty and government authoritytheir profile, for instance, appears on currency, and their portrait in government buildings. The Sovereign is further both mentioned in and the subject of songs, loyal toasts, and salutes. "God Save the King" (or, alternatively, "God Save the Queen") is the British national anthem. Oaths of allegiance are made to the Sovereign and their lawful successors. The monarch takes little direct part in government. The authority to use the sovereign's formal powers is almost all delegated, either by statute or by convention, to ministers or officers of the Crown, or other public bodies. Thus the acts of state done in the name of the Crown, such as Crown Appointments, even if personally performed by the monarch, such as the King's Speech and the State Opening of Parliament, depend upon decisions made elsewhere: Legislative power is exercised by the King-in-Parliament, by and with the advice and consent of the House of Lords and the House of Commons. Executive power is exercised by His Majesty's Government, which comprises ministers, primarily the