[2] The United Kingdom is the only country of the Big Four which is not a member state of the European Union, having ended its membership in 2020, pursuant to a referendum held in 2016.

With US President Barack Obama, for example, they discussed the Transatlantic Trade and Investment Partnership, the Syrian civil war and the use of chemical weapons during the conflict,[7] the Russian annexation of Crimea and international sanctions against Russia,[8] the post-civil war violence in Libya,[9] the Israeli–Palestinian conflict,[10] the 2014 American intervention in Iraq and the Ebola virus disease.

France, Germany, Italy and the United Kingdom have been referred to as the "Big Four of Europe" since the interwar period (1919–1939), when the four countries signed the Four-Power Pact and the Munich Agreement.

[4] Britain and France, permanent members of the League of Nations' executive council along with Italy and Japan, were involved in a policy of appeasement towards Germany.

The British government triggered Article 50 of the Treaty on European Union to begin the process to leave the EU, which concluded on 31 January 2020.