Sir John Major KG, CH, PC , is a former British politician who was Prime Minister of the United Kingdom and Leader of the British Conservative Party from 1990 to 1997. During his time as Prime Minister, the world went through a period of transition after the end of the Cold War. This included the growing importance of the European Union and the debate surrounding Britain's ratification of the Maastricht Treaty. As Prime Minister, Major and his government were also responsible for the United Kingdom's exit from the Exchange Rate Mechanism after Black Wednesday on 16 September 1992.