Graham Farrell is Professor at the Centre for Criminal Justice Studies, School of Law, University of Leeds. He has published many studies relating to Crime Science. He has been fortunate, both professionally and personally, to know and learn from Nick Tilley for 25 years, including the last decade or so researching the international crime drop together.

Aiden Sidebottom is Senior Lecturer at the Jill Dando Institute of Security and Crime Science, University College London. His main research interests are situational crime prevention, problem-oriented policing and programme evaluation. He recently co-edited the Handbook of Crime Prevention and Community Safety (2nd edition, with Nick Tilley).