If Lauterpacht, writing back in 1950, warned about the changing landscape of the law of immunities due to the increased activities of the state in the economic sphere, English courts have never been so busy with regards to the enforcement of foreign arbitral awards against sovereign states today. As foreign direct investment grows, so too does the number of disputes between states and investors. Increasingly these disputes are resolved by international arbitration proceedings but once resolved, the enforcement of awards against states brings its own challenges. Whilst enforcement of arbitral awards should be 'almost a matter of administrative procedure' (to use the language of PetroChina International (Hong Kong) Corp Ltd [2011]), immunities remain to some, a 'hurdle', adding complexity to that process. This book gives the reader the key to understanding the principles governing such a notion in the context of enforcement of arbitral awards. This is the first systematic treatment of the jurisprudence relating to award enforcement against foreign states in England. It provides comprehensive examination of the principles and case-law relating to state immunity in the context of enforcement of international arbitral awards before English courts. It addresses questions such as: What are the principles governing the enforcement of international awards against sovereigns in England? How does the distinction between jurisdictional immunity and enforcement immunity operate in this context? What are the precise contours of such legal notions when they are put into motion by means of procedure? What is the practice of English courts in that regard? This book also covers the complexities arising from enforcement proceedings in other jurisdictions and their relation to proceedings in England. Authored by an expert with unique insight into immunities both as a practising barrister and as an academic, this is an essential resource for anyone interested or involved in enforcement proceedings during which state immunity is invoked.