Opera and psychiatry both provoke lively debate and strong opinions. Opera can be regarded as far removed from the real world; but, as I have shown, a psychiatric assessment of these twelve disordered heroes demonstrates how credible they actually are. Personality disorder is a particularly controversial diagnosis as it is not classified as a mental illness: these men illustrate some of the diagnostic challenges, and I hope I have been able to dispel some of the related myths and misconceptions. Although I have described various categories of personality disorder and their recognised traits, it is not in order that they can be simply learnt and identified. This book bears no relation to the writer and documentary-maker Jon Ronson's recent The Psychopath Test, a popular book that teaches the reader how to spot psychopaths using Hare's 20-item Checklist. In clinical practice one rarely needs to be so specific. The diagnostic formulation is not about compiling a list of traits; it arises, as I have emphasised, out of a full assessment of the person – ensuring that all the possible information is obtained and excluding any physical conditions that might influence the person's mental state. Ronson's book is intentionally amusing, but assessment is, of course, a very serious and responsible process. We are individuals and not diagnostic categories, and people don't always behave in ways that we anticipate. Six of my twelve operatic heroes commit suicide, and all but one of them die. Most of these tragedies could probably have been predicted, just as they could probably have been prevented if some form of intervention or psychiatric treatment had been instituted before it was too late. But, as we said at the outset, this is opera, not real life.

Being a psychiatrist does not mean that one has any special knowledge of the human mind, or that one can analyse any person one meets. How much more challenging – and unrealistic – is it, therefore, even to try and assess a character from opera! But, as I have shown, it is still possible to build up a picture, not just from the available sources, but also from watching and listening to the singer, as well as to the accompanying music in the orchestra.