Queen Elizabeth II, or Elizabeth Alexandra Mary of the House of Windsor, was the reigning monarch of the United Kingdom and the head of the Commonwealth. She was the longest-serving monarch in British history, having served for nearly 70 years. She had presided over some of the momentous changes in her country’s history, including the end of the British empire, a number of royal scandals, several wars, and the U.K. joining the European Union and then leaving it after the Brexit referendum.