To understand the success of Harris’s book, we must look at the trail blazed by his mentor, Eric Berne. Berne’s Games People Play, published three years earlier, was a surprise hit which brought academic psychology to a mass audience.

Berne had developed something called ‘transactional analysis’. It was a boring term for an exciting concept, reversing the Freudian tradition that saw the world as ‘I’ or ‘me’-centred. For Freud, other people were not important as people - they were merely one’s ‘object relations’. Berne reacted against this, elevating relationships to the high table of study. He believed that an encounter between two or more people, a ‘transaction’, was psychotherapy’s elusive unit of analysis. Instead of asking a subject about themselves (as in psychoanalysis), one could determine the problem simply by being a witness to what is actually said or done in the course of a transaction.

The ‘games’ that people played were like worn-out loops of tape we inherited from childhood, yet continued to let roll. Though limiting and destructive, they were also a sort of comfort, absolving us of the need to really confront unresolved psychological issues. Berne’s brand of psychotherapy involved asking the client what he or she wanted ‘fixed’ and proceeding to fix it. There was no assumption of underlying malaise. This new approach was of course the essence of self-help.

Harris used Berne’s work as a basis for his own, but instead of analysing the games we play, focused on the internal voices that speak to us all the time in the form of archetypal characters: the Parent, the Adult and the Child (the PAC framework). All of us have Parent, Adult or Child ‘data’ guiding our thoughts and decisions, and Harris believed that transactional analysis would free up the Adult, the reasoning voice. The Adult in us prevents a hijack by unthinking obedience (Child), or ingrained habit or prejudice (Parent), leaving us a vestige of free will.

Transactional analysis may not be a household term, but in some minds it lived on. James Redfield has acknowledged Harris and Berne as crucial influences when he came to write one of the biggest-selling books of the 1990s, The Celestine Prophecy. The ‘control dramas’ that his characters engage in, and seek to be free of, are squarely based on the games and positions of transactional analysis; the survival of the book’s characters in fact depends on their ability to see beyond these automatic reactions.

Certainly, the Adult in Burns’ book can be equated with the ‘higher self’ that forms the centrepiece of so much self-help and New Age writing. Awareness of, and reliance on, this internal voice is a secret that all successful people share.