Once the required number of matched prisons pairs was fixed, the randomization was done within pairs in which eight prisons from each pair were randomly assigned to the intervention and the remaining to the control group. One of the investigators from Maastricht University who didn't have information about the study prisons performed the randomization by consulting the online randomization website; random.org. The investigators will then undertake follow-up and monitoring for a year (from March 2016 to April 2017) and outcomes will be measured 3.3.1. Procedure