While a book may be written by an individual, it almost always involves the contribution of many people. This is definitely the case with this one. Sections are based on fieldwork with ‘hard to reach’ groups, in some cases members of proscribed organizations or supporters of jihadism, demanding extensive periods of fieldwork and relationship building. Here my co-worker Mohammad Ilyas has been critical in nurturing relationships over several years, building on earlier work made possible by an Australian Research Council Discovery Grant and a European Union Marie Curie International Fellowship. Opportunities to explore ideas and make sense of often confusing material were fundamental to the book’s construction, and here the generosity of others has been critical. Colleagues and students in the Department of Criminology and Sociology at Middlesex University in London provided invaluable opportunities to explore ideas, and it would not have been possible to complete this book without the support of my Dean, Joshua Castellino. I have been able to explore key themes at the Centre d’Analyse et d’Intervention Sociologiques at the Ecole des Hautes Etudes en Sciences Sociales in Paris, where readers will note my debt to Farhad Khosrokhavar, François Dubet, Michel Wieviorka and Alain Touraine. Research Committee 47 of the International Sociological Association, led by Geoffrey Pleyers, afforded me opportunities to make sense of material at critical points. Others have also engaged in generous dialogue, from colleagues at the Catholic University of Louvain in Belgium and Aarhus University in Denmark, to practitioners involved in the EU Radicalisation Awareness Network (RAN) and the European Expert Network on Terrorism Issues (EENeT). I have greatly benefited from advice about ethical issues, in particular that of my colleagues Sarah Bradshaw and Philip Leach at Middlesex University. David Anderson QC, at the time the United Kingdom’s Independent Reviewer of Terrorism Legislation, generously responded to ethical as well as legal questions posed by the research this book is based on. The book itself owes a great debt to the generous feedback of anonymous reviewers at Polity, and to the patient but demanding engagement of Jonathan Skerrett. Despite all this, it goes without saying that I alone am responsible for the judgements, arguments and conclusions presented in the chapters that follow.

The research upon which this book is based, whether interviewing or analysing social media material, has at times been difficult not only intellectually but personally. While sociological work can sometimes celebrate life-affirming experiences, this is not the case in this book. Undertaking this research has underlined just how much our human vulnerability and incompleteness is not a problem to be overcome but the very basis of living with others. Throughout this period, I have relied on the presence of many people constantly affirming the complexities and wonder of life – above all Lorna, to whom this book is dedicated.