In this book, leading scholars of EU law, judges, and practitioners unpack the judicial reasoning offered by the UK Advocates General in over forty cases at the Court of Justice, which have influenced the shape of EU law. The authors place the Opinions in the wider context of the EU legal order, and mix praise with critique in order to determine the true contribution of the UK Advocates General, before hearing the concluding reflections by the UK Advocates General themselves. The role of Advocates General at the Court of Justice of the European Union remains notoriously under-researched. With a few notable exceptions, not much ink has been spilled on analysing their contribution to the judicial discourse that emerges from the Court’s Palais in Luxembourg. More generally, their impact on the shaping of EU law is only sporadically explored. This book fills the lacunae by offering an in-depth analysis of the way in which the UK Advocates General contributed to development of EU law during 47 years of the UK’s membership of the EU. During their terms of office, Advocates General Jean-Pierre Warner (1973-1981), Gordon Slynn (1981-1988), Francis Jacobs (1988-2006), and Eleanor Sharpston (2006-2020) delivered over 1400 Opinions. This staggering contribution of the four individuals and their cabinets of legal secretaries was supplemented by an Opinion of a then Judge of the Court of First Instance, David Edward, who was called to act as an Advocate General in two joined cases in what is now the General Court. With the last UK Advocate General departing from the Court of Justice in September 2020, an important era has ended. With this watershed moment, it is apt to take a look back and critically analyse the contribution to development of EU law made by the UK Advocates General, and to elucidate the lasting impact they have had on the nature of EU law.