Impostor syndrome was first described in 1978 by the psychologists Pauline Rose Clance and Suzanne Imes. It is now such a common phenomenon that organisations all across the world run seminars and symposia on how to combat it. Characterised by Clance and Imes as an ‘internal experience of intellectual phoniness’, it leads intelligent people to think they are not intelligent. In fact, ‘they are convinced that they have fooled anyone who thinks otherwise’.

Academics are particularly susceptible to impostor syndrome, and it is not hard to see why. On the one hand, they claim to be able to explain the apparently inexplicable: the Big Bang, the Reformation, Brexit. On the other hand, they exist in a world of often cruelly exacting assessment, with their every publication read, re-read and sometimes eviscerated by anonymous reviewers. Given the disjunction between aspiration and reality, it is little wonder that they might come to doubt themselves.

Yet in a world in which everyone fears they might be an impostor, how do you tell who is faking it and who is not? This was a question that transfixed the historian Hugh Trevor-Roper throughout his career. It sustained his furious attacks on such colleagues as Lawrence Stone, whom he believed to have stolen and fabricated historical research. It also led him to write compellingly about real frauds, including the fantasist Edmund Backhouse, whose almost entirely fictional and luridly pornographic memoir formed the basis of one of Trevor-Roper’s books.

In 1958, another impostor entered Trevor-Roper’s life. At that point, he was claiming to be the Reverend Robert Peters, a highly qualified and recently married postgraduate student at Magdalen College, Oxford. Further investigation revealed, however, that his name was not Peters, that he had been stripped of holy orders, that his qualifications were false and that his marriage was bigamous. Only his status as a postgraduate student was true – and the discovery of these malfeasances soon ended that.

There the story might have ended too, but Trevor-Roper was intrigued, opening a file on Peters and gathering further information about him. Peters, for his part, was unabashed, continuing to embellish his nonexistent credentials, claim ever more exalted ecclesiastical titles and acquire a number of wives. Still more intriguingly, he continued, like a mobile Walter Mitty or an academic Zelig, to reappear in Trevor-Roper’s professional life for the next half-century.

Adam Sisman has used the collection of notes Trevor-Roper put together on Peters over this period and supplemented it with his own research to produce a wonderfully entertaining account of this academic and clerical fraud. He follows him from lie to lie, job to job, marriage to marriage, continent to continent. Again and again, Peters came close to success and even stability, securing posts at schools on both sides of the Atlantic, the parochial cure of people in Scotland and South Africa, and positions in universities from Cambridge to Canada and from New Zealand to Nigeria. Always, he was found out and then run out of town, only to start again elsewhere.

Throughout it all, Peters was unashamed and evidently unshamable, an impostor who wholly inhabited his fabrications and who indignantly repudiated anyone who doubted him. But he was sustained in his career by other people who seemed to believe in him, at least for a time. This group included some, though not all, of his wives and a surprisingly large cast of established scholars. Perhaps constitutionally attracted to someone so unlike themselves in self-confidence, perhaps genuinely keen to give an apparently able man a second chance, a certain sort of academic was all too easily taken in by Peters.

For Trevor-Roper, who took a dim view of his own profession, this was all hilarious stuff. It became rather less funny when he himself was fooled by a set of forged documents that had been passed off as Hitler’s diaries. Significantly, he appears to have stopped collecting material on Peters at about the same time.

The Professor & the Parson is a fantastic read and fully deserves to be among everyone’s books of the year. It is full of wonderful stories and splendidly comic moments. It is also beautifully written. And yet there is clearly more to be said. A sad little footnote records that, only last year, Peters’s son advertised for information about ‘Professor Robert Peters’. It would be fascinating to know more about his life and the lives of all the seven or eight women that his father apparently married.

Although the conclusion to the book is unobjectionable, it might easily have been pushed further. Peters, Sisman contends, suffered from a condition called narcissistic personality disorder. Sufferers, it seems, have ‘an exaggerated sense of self-importance’: they expect ‘to be recognized as superior even without achievements that warrant it’. It is, in other words, the diametrical opposite of impostor syndrome, and it appears a suitable explanation for much of Peters’s behaviour. But it is surely not the whole story. His was a very specific example – one that speaks of a particular moment in time. Who seeking status today would pretend to be an academic, much less a priest? That of course begs further questions. What would someone like Peters do today? Which professions now appeal to narcissists? Somewhere, one hopes, another, equally interesting file is being opened. But where?