"The demographic makeup of the police compared to the population policed has always been seen as a key factor in the legitimacy and effectiveness of policing. As this vital book discusses, in the recent decades of increasing socioeconomic and cultural conflict, police legitimacy has been in a state of permanent crisis. Closing the gap between the population and police in terms of ethnicity, gender, sexuality and education has been one of the most commonly suggested reforms. This book offers a comprehensive analysis of the likelihood that increasing police diversity could significantly enhance their legitimacy in particular by changing traditional police culture. It covers the recent debates and research on this issue comprehensively and lucidly. An impressive scholarly achievement, it will be of great value to police scholars, practitioners and policy makers." Robert Reiner, London School of Economics and Political Science.