Surely there has never been a historian who was elected an Honorary Fellow of both the Royal College of Psychiatrists and the Royal College of Physicians. In this, as in so many things, Roy Porter was unique. Yet he once said to me — and no doubt to many others — ‘I'm not really a medical historian. I'm a social historian and an 18th century man’.

Roy's achievements and life — only 55 years unfortunately — have been extensively set out in the obituaries that appeared in all the serious newspapers. These facts were also eloquently expressed in the encomia given at his memorial service on 22 April 2002 at St Pancras Parish Church, packed by those who knew him, had been taught by him, had heard his lectures or had at least read some of his unique literary output. The admissions' tutor from his Cambridge college told how Roy's scholarship papers had gained the highest marks ever known to his examiners. Yet he had not come from any intellectual hothouse.

By origin, Roy was a working-class cockney, born in 1946 and raised in a warm but crowded family home, lacking in all mod cons. In a delightful introduction to his London: A Social History, he described this ‘stable, if shabby, community…. undiscovered by sociologists’. From there, the family moved to a semi with indoor toilet which, in the 1950s, was definitely going up in the world. At his grammar school (would he have done so well in a comprehensive?), Roy was fortunate to come under the influence of an exceptional English master, although on arrival at Cambridge, he switched to history. He was recognised quickly as an outstanding student and mopped up the predicted double first.

He was then influenced by the psychoanalyst and scientific historian, Bob Young, founder of the Free Association Books, to study the 18th century history of geology, resulting in his first book, The Making of the Science of Geology. After this, he became Fellow, Director of Studies and — astonishingly for one so unconventional — Dean of Churchill College, with heavy teaching and administrative duties. Meanwhile, books began to appear on the history of environmental sciences, 18th century science and the Enlightenment. A wish to have more time for research and writing then led to his move to the Wellcome Institute for the History of Medicine, first as Senior Lecturer and then as Professor.

It was there, particularly in association with Professor Bill Bynum, that his interest turned to the history of psychiatry. Their first edited product, together with the late Michael Shepherd, was a trilogy, The Anatomy of Madness. Today, its contents give a very uneven impression but, in fact, it opened a new era in the serious professional historiography of psychiatry. It also provided a launching pad for a new generation of historians of the subject, some of whom were psychiatrists. One of Roy's personal works, Mind Forg'd Manacles, which was a history of madness from the Restoration to the Regency, followed next, and clearly established his reputation. His literary output then began to assume Stakhanovite proportions.

Once asked what he was currently writing, Roy replied ‘14 books’. It was neither an exaggeration nor a boast, but simply a fact. How he did it will probably never be clearly understood, though he certainly slept very little. One house guest who came down to his kitchen in the middle of the night found Roy deep in the works of Aristotle. Perhaps he had mild hypomania, without any of the pathological features. Practically every photograph of Roy that has appeared since his death has shown him with a wide and mischievous grin. Most people would feel more cheerful after even a casual conversation or telephone call with him.

Among the books that emerged in breathtaking succession were those on A Social History of Madness (up to the Regency), Gibbon, quackery in England, medicine in the 18th century, Enlightenment: Britain and the Creation of the Modern World, an encyclopaedia of the history of medicine, a social history of London, a medical history of mankind and a dictionary of 18th century history. Other publications are too numerous to mention and are to be found in many academic journals.

On top of this, he was a prolific reviewer of books, a regular broadcaster and a ubiquitous lecturer, rarely refusing an invitation, however humble or remote the audience. The two qualities that have been most often stressed since Roy's death were his kindness and his generosity; whatever his commitments, colleagues or students never came to him in vain for help or advice. I was once astonished to receive a note of congratulation from him about a book review I had written in a fairly minor journal. It was the sort of kind action one often thinks of, but does not get round to doing.

With German Berrios, Roy was a founding editor of the journal History of Psychiatry, the first one to be devoted to the subject. He was also Editor for many years of History of Science. Some time after the Wellcome Institute moved to University College London, while still at the height of his powers, Roy surprisingly took early retirement and moved to the Sussex coast. His intention, he said, was to have more time for writing and travelling, to cultivate his allotment and learn to play the saxophone — he was a great jazz enthusiast.

Great historian though he was — in the opinion of his peers — it would be impossible to write anything about Roy without trying also to portray the person. With facial hair that oscillated between a beard and ‘designer stubble’, a shirt generously unbuttoned, a gold medallion or even an earring, jeans and cowboy boots, Roy was scarely the picture of a reclusive scholar. He enjoyed good living in every form and enlivened every gathering he attended. Fame had not brought him riches though; he was unworldly about finance and his travel was by train or bicycle. His long-suffering literary agent found, when she took him on, that he had already signed 29 publishing agreements, few of which would bring him any significant monetary income. His personal life can be best described as eventful; he was divorced four times — possibly a record outside Hollywood.

We had one disagreement when he contributed to a volume that was being edited by German Berrios and myself. Characteristically, his own chapter was one of the first to come in; it was stimulating and stylistically admirable. In writing about the 1920s, though, he praised the part of Virgina Woolf's Mrs Dalloway in which she sarcastically describes the intervention of a fashionable psychiatrist (based on Sir George Savage, who had treated her). But, I asked him, what would you have done if you had been the psychiatrist in 1923, with the options available then? For once, he had no ready answer and we agreed on a compromise text. Perhaps there is really no substitute for the actual experience of clinical responsibility, even for one so learned and full of human sympathy.

Roy died suddenly, while cycling from his allotment in St Leonards. Work on the history of psychiatry will never be the same without him.