The United Kingdom's referendum on continued EU membership, held in June 2016, resulted in "BREXIT". Since then Great Britain and the European Union are trying to unravel a more than 40 years relationship characterized by ups and downs. This book presents an overall picture of that relation including its peculiarities. It seeks to analyse and discuss the drivers and origins leading to "BREXIT" by focusing on the historical evolution from the birth of the Union in 1950 until the beginning of UK's secession negotiations in 2017. The book explains the steps of withdrawal, the legal framework as well as possible implications for the United Kingdom and the European Union.