This book studies the history of diplomatic and security relations between Ireland and Britain, giving context to the role of Anglo-Irish relations in the early years of the Northern Ireland Troubles. Looking at the wide variety of relations and the deep trust evidenced by cooperation in the 1960s, author Tony Craig shows for the first time the context of Common Market and trade negotiations in which Anglo-Irish relations crystallized in the era of Lemass. As Anglo-Irish relations change, so too does the nature of the book. Once the first British soldiers are killed, and following the deaths of so many civilians on Bloody Sunday, joint entry to Europe became little more than an afterthought. Thus, new research on the attempts by Britain to gain security and intelligence cooperation with the Republic alter previous judgements of how the Republic reacted to the emergence of the Troubles. Despite the Sunningdale Agreements, this book shows that after 1974 both Britain and Ireland began se