Why are the British Not Part of the Euro?

One of the only European currencies that is not included as part of the Euro is the British Pound Sterling. Why did the UK decide to abstain from the European Common Market? This could be the subject of many lengthy case studies, but the bottom line is that the British currency is one of the oldest and most well-known currencies in the market today. It is one of the currencies used as a standard. The British pound is now worth roughly 2 U.S. dollars, and is one of the benchmark currencies in the world today.