For readers with an insurance or commercial background, this book provides a high-level accessible introduction to the rules that govern the legal relationship between the parties to reinsurance contracts while simultaneously presenting a concise, in-depth analysis of contemporary developments for specialist and non-specialist readers alike. This is the first book to approach the analysis of the legal relationship between the parties through the lens of the balance of interests between reinsurer and reassured: while the Insurance Act 2015 was introduced to redress the former imbalance of interests between assured and insurer, it applies equally to reinsurance contracts. A text of this size must be selective about the range of legal rules it focuses on. The book is divided into six chapters: the presumption of back-to-back cover, Follow the Settlements clauses, damages for late payment of claims, claims clauses, the aggregation of losses, and the allocation of losses. These guide the reader through the main components of the parties’ legal relationship, focussing on two recent reforms – section 13A and, to a lesser extent, section 11 of the Insurance Act 2015 – as well as contemporary developments including the aggregation of Covid-19 business interruption losses and the allocation of losses viz The Fairchild Enclave at the reinsurance level. Written for legal professionals with a connection to, or at least some prior knowledge of, the insurance industry, and recognising that overseas courts frequently refer to English law as representing international market practice, this book will find many readers worldwide including legal practitioners, industry professionals, and scholars.