The Suez Crisis, or the Second ArabIsraeli war, also called the Tripartite Aggression (Arabic: , romanized: Al-Udwn a-uliyy) in the Arab world and the Sinai War in Israel,

was an invasion of Egypt in late 1956 by Israel, followed by the United Kingdom and France. The aims were to regain control of the Suez Canal for the Western powers and to remove Egyptian president Gamal Abdel Nasser, who had just nationalised the foreign-owned Suez Canal Company, which administered the canal. After the fighting had started, political pressure from the United States, the Soviet Union and the United Nations led to a withdrawal by the three invaders. The episode humiliated the United Kingdom and France and strengthened Nasser.On 26 July 1956, Nasser nationalised the Suez Canal Company, which prior to that was owned primarily by British and French shareholders. On 29 October, Israel invaded the Egyptian Sinai. Britain and France issued a joint ultimatum to cease fire, which was ignored. On 5 November, Britain and France landed paratroopers along the Suez Canal. Before the Egyptian forces were defeated, they had blocked the canal to all shipping by sinking 40 ships in the canal. It later became clear that Israel, France and Britain had conspired to plan out the invasion. The three allies had attained a number of their military objectives, but the canal was useless. Heavy political pressure from the United States and the USSR led to a withdrawal. U.S. president Dwight D. Eisenhower had strongly warned Britain not to invade; he threatened serious damage to the British financial system by selling the US government's pound sterling bonds. Historians conclude the crisis "signified the end of Great Britain's role as one of the world's major powers".The Suez Canal was closed from October 1956 until March 1957. Israel fulfilled some of its objectives, such as attaining freedom of navigation through the Straits of Tiran, which Egypt had blocked to Israeli shipping since 1948-50.As a result of the conflict, the United Nations created the UNEF Peacekeepers to police the EgyptianIsraeli border, British prime minister Anthony Eden resigned, Canadian external affairs minister Lester Pearson won the Nobel Peace Prize, and the USSR may have been emboldened to invade Hungary.

The prime minister of the United Kingdom is the head of government in the United Kingdom. The prime minister advises the sovereign on the exercise of much of the royal prerogative, chairs the Cabinet and selects its ministers. As modern prime ministers hold office by virtue of their ability to command the confidence of the House of Commons, they sit as a member of Parliament.

The office of prime minister is not established by any statute or constitutional document, but exists only by long-established convention, whereby the reigning monarch appoints as prime minister the person most likely to command the confidence of the House of Commons; this individual is typically the leader of the political party or coalition of parties that holds the largest number of seats in that chamber. It was announced by Prime Minister Boris Johnson on 31 January 2022 that the office of Prime Minister would be formally established.The prime minister is ex officio also First Lord of the Treasury, Minister for the Civil Service and the minister responsible for national security.: p.22  Indeed, certain privileges, such as residency of 10 Downing Street, are accorded to prime ministers by virtue of their position as First Lord of the Treasury. In 2019, the office of Minister for the Union was established; Boris Johnson became the first prime minister to hold this title.