We present a process evaluation of a new anger control intervention within an urban remand prison in London, UK. An anger control group was created and run as an extension of the prison in-reach healthcare team, in order to meet the needs of prisoners. We evaluate the aims of the intervention, therapeutic methodology, administrative process, and post-intervention outcomes. We report change in anger scores (State Trait Anger Expression Inventory; STAXI-II), showing how a service of this type might deliver important benefits. Through the use of a focus group with the clinicians who ran the service, we have reflected on this process to inform the evaluation. We conclude that anger management may have a useful role in remand prisons, not just for violent offenders, but as part of a wider public health agenda. Resources for new prison healthcare groups are scarce, particularly in urban remand prisons, and clinicians may have to collaborate with other teams to provide a range of interventions. Following the expressed needs of the prisoner population promotes a strong uptake of clients. Prison health services operate within a complex and environment which restricts healthcare teams' ability to run groups. We provide recommendations on overcoming potential barriers to care.