In that distant time when people on aeroplanes used to talk to each other, I’d sometimes get asked what I did for a living. ‘I’m a psychiatrist and psychotherapist who works with violent offenders,’ I would reply. Mild curiosity would shift to amazement. ‘But surely those people can’t be helped, can they? Aren’t they born that way?’ Some would call it ‘a waste of time’ to bother with ‘such monsters’; the occasional British fellow traveller might offer, sotto voce, ‘Frankly, I think Parliament ought to bring back hanging.’ Nowadays, if anyone starts up a chat while we’re fastening our seatbelts, I’m inclined to tell them I’m a florist.

But I’ve started to feel a sense of urgency about coming forward to offer a better response to questions of how and why I do this job. Listening to people articulate how they came to commit unspeakable acts of cruelty and working to help them take responsibility for their actions, I’ve learned some powerful lessons about human nature. In thirty years of tremendously rewarding and often unpredictable encounters with ‘those people’, I’ve been privileged to witness the amazing capacity of our minds for change.

In this moment of increasing polarisation and othering, I believe there’s comfort and hope to be found in these narratives, which at first glance may seem to be about ‘those people’ we most fear, but which gradually reveal a common humanity. In each chapter, I invite you into the room with me to show you what I’ve seen and heard at the extremes of human experience. In doing so, I hope to turn the deep suffering lived and caused by the unfortunate few into narratives that contain value for the many. Despite their differences, every patient represented here reveals how good and evil, right and wrong, and labels of victim and perpetrator are not set in stone and may coexist.

The Latin proverb that gives this book its title suggests that the devils we know are less risky than the ones we don’t. By getting up close to the unknown and the feared, I believe you will find, as I have, that we are more alike than we are different. I realise that accepting our common humanity with ‘monsters’ may be hard for the reader – it has been for me. To paraphrase the beautiful words of Lear’s daughter, ‘We ever but slenderly know ourselves.’

Every violent crime is a tragedy for all who are involved. I am not here to argue that any such action should be excused, or that our prisons and secure hospitals should be emptied. While I think we imprison far too many people, essentially to feed the public appetite for revenge, I have no doubt that a subgroup of violent offenders will have to stay in secure settings long-term. I also understand that revenge is human and natural, but it can keep us stuck in our fear and anger, mirroring the very cruelty we condemn as ‘evil’.1 There is wisdom in the popular notion that hating someone else is like taking poison and waiting for them to die. And as Gandhi and others have observed, it is a measure of a just society that we treat the worst among us with compassion. That’s where forensic psychiatry comes in.

Back when I was in medical school in the 1980s, psychiatry was still a specialism that was often discounted, despite the evidence, known since classical times, that a healthy mind is essential to a healthy body. (And a healthy society too – as a colleague of mine likes to say, ‘Psychiatrists are doctors who look after the only part of the body that votes.’) As a student, I briefly considered pursuing orthopaedic surgery, probably because I wanted to fix things and was attracted by its pragmatic effectiveness. But psychiatry drew me in because I saw that the complexity and power of the human mind were immense and that changing minds had significance both personally and politically. When I started out, I thought the task was to make people feel better, but time has taught me that it is about helping them to better know their minds, which is quite another matter.

In those days, the prevailing metaphor was that of the mind as a computer, a machine where identity is hard-wired. Thoughts and emotions are ‘processed’ and ‘filed’; we ‘switch modes’ or ‘default’ when carrying out different functions. But after many years, I’ve come to think of the mind as a coral reef: ancient, layered and mysterious, not without shadows and risk but containing nourishing diversity. It might appear chaotic, but it is a structured ecosystem, endlessly fascinating and essential to life. Under environmental stress, reef systems may bleach out and wither, but we’ve also seen how they can be responsive to certain interventions and made more resilient. The exploration of the mind that I embarked on as a student, and which I continue every day, requires a deep dive into a darkness where things of great beauty as well as danger might appear. This can be a turbulent process for both me and my patients; I have no hesitation in admitting it took time and effort to acclimatise myself and learn to breathe easy.

The word ‘forensic’ derives from the Latin forum, a place to hear legal disputes. Beyond providing assessments, making diagnoses and co-ordinating the care of patients like any other medical specialist, forensic psychiatrists address how a society responds to and treats those people who break the criminal law. The work raises many ethical and legal questions about responsibility, agency and blame for actions done when people are mentally unwell. Those of us who work in secure hospitals are members of a team providing co-ordinated care, as I have done for most of my career. Not unlike ‘dive buddies’, we discuss a plan and share responsibility for each other’s safety. Forensic work has been an ideal choice for me: I am by nature a collaborator, as borne out by my favoured work as a group therapist and my co-authoring this book.

I’ve spent my working life employed by the National Health Service. As many readers will be aware, the NHS was founded after the Second World War on the principle that health care should be provided by the state and funded from the public purse, because all citizens benefit from a healthy population. But as costs have risen and people live longer, successive governments have moved the NHS towards a more market-based model to cope with demand. References to NHS ‘trusts’ in the pages that follow signify the individual business units (much like the US model of HMOs) that were set up following a massive restructuring in 2001. Today, the UK, like so many other countries, struggles to provide good enough mental health care. It is the urgent task of our time to consider how we can rebalance priorities and recognise the huge social and human benefits of caring equally for the mind and body.

My colleagues and I have to live with knowing that we work in a flawed and compromised system, especially in prisons, where the demand for mental health care far outstrips capacity. We are part of a democracy, where people vote for governments whose policies, including mass incarceration, reflect the will of a majority. Although convictions for criminal violence have fallen since I began my medical training, more people are being sent to prison for longer. With rates higher in England and Wales than anywhere else in western Europe, the number of incarcerated people needing mental health care has also risen.2 Unfortunately, about 70 per cent of prisoners are estimated to have at least two mental health issues, which means that every time I work with one distressed person in prison, I know there are many more like them whom I will never reach. That doesn’t mean I can throw up my hands in protest and walk away; all doctors go towards suffering and make what difference they can.

Over the course of the last three decades, I’ve spent time working in prisons and the community, but for the most part I’ve been based at Broadmoor Hospital in Berkshire, about fifty miles west of London. Built in 1863 as part of a Victorian system of asylums (from the Greek, meaning ‘refuge’), these were venues where ‘criminal lunatics’ could be cared for, sometimes indefinitely. Its original mock-Gothic appearance and a history of housing some of Britain’s most notorious criminals led Broadmoor to hold a particularly lurid position in the public’s imagination. But today, places like Broadmoor are no longer seen as oubliettes for people who are condemned and rejected; they care for patients who generally make progress, and the average stay is five years. When I joined the staff, there were around six hundred male and female patients being treated in the red-brick complex. It now houses only two hundred men in new, modern buildings and, truthfully, it looks more like a small regional airport than the stuff of nightmares. Most of the patients I see there are either committed by a judge after trial or transferred from prison for treatment if their mental health has deteriorated.

Over the years, I’ve come to think of ‘these people’ as survivors of a disaster, where they are the disaster. My colleagues and I are the first responders, meeting them at a turning point in their lives and help them to come to terms with a new identity, which may feel indelible. As one of my patients memorably put it...