Jonathan Sumption is a former History Fellow of Magdalen College, Oxford. He is the author of Pilgrimage and The Albigensian Crusade, as well as the three volumes in his celebrated history of the Hundred Years War: Divided Houses, Trial by Battle and Trial by Fire. He is also a practicing QC, well-known for his defence of the Government before the Hutton Inquiry, and other high-profile cases before the courts.

Mark Thwaite: What first fascinated you about the Hundred Years War Jonathan?

Jonathan Sumption: The interlinked stories of England and France in the late middle ages have fascinated me ever since I first encountered them reading for a history degree at Oxford, and then teaching undergraduates as a young academic.

Mark Thwaite: And why was the fascination so strong?

Jonathan Sumption: The first thing that struck me about the Hundred Years War, as I think it strikes most people who read about it, is the dramatic scale of events. The war was originally provoked by the age-old conflict between the French and the English rulers about the provinces ruled by the Kings of England in south-western France. The English were determined to maintain their independence in the region, while the French were equally determined to integrate the possessions of the English house into an increasingly centralised state. From these beginnings was born a struggle lasting in fact well over a hundred years, from the beginning of the fourteenth century until the second half of the fifteenth, to which the two countries devoted much of their wealth and reduced themselves to ruin. All of their neighbours, Scotland, Flanders, Germany, Italy, Spain and Portugal were progressively drawn into it by the play of interests and alliances. By the fifteenth century, the war had outgrown its origins, and become a struggle for control over France itself.

Whether we like it or not, war has been the chief collective enterprise of mankind until quite recently. War is destructive and inhumane. Yet it has shaped human institutions. It has stretched human experience and human capabilities. By comparison, long periods of stability have commonly been characterised by mediocrity and decline. As Shakespeare recognised two centuries later, both England and France derived their national identities from this tremendous struggle. But what is perhaps most fascinating about this war is that for the first time in European history, we can follow these changes not only through the actions of kings and princes, but through the experiences of the humblest archer or foot-soldier. Their lives are recorded in a remarkable array of sources, not only chronicles but memoirs, records, poetry and novels, some of them intensely personal.

Mark Thwaite: Divided Houses is the third volume of your mammoth study of the war. How long did it take to write this volume?

Jonathan Sumption: Each of the three volumes so far has taken me about ten years. It is a long time, I know. But it has to be, because since leaving academic life in the 1970s I have earned my living as a barrister, practising in the courts. The bar is an exceptionally demanding profession. There was a time, at the beginning, when I seemed to be writing the book it at about the same speed as it was fought, and began to worry about my longevity. In spite of appearances, I have speeded up. I know my way around the sources better than when I began. I have a better instinct for what material will prove fruitful and what will not. There will be two more volumes, which will be shorter than the latest one, and will be completed rather quicker. I have done a fair amount of the research for them already.

Mark Thwaite: Your books must take huge amounts of research; do you enjoy the research or are you always keen to get down to the actual writing?

Jonathan Sumption: I enjoy the research, of course, or I would not be doing this. I enjoy the cities where great archives and libraries tend to be. I enjoy the direct contact with my forbears: the feel of old vellum under my fingers, or rat-chewed fragments in French provincial archives, or unpicking the strap around the very notebook which an officer of the English garrison at Calais carried on his rounds about the town. But the writing is the ultimate objective. The researcher is omnivorous, but the writer has to be selective. You have to guard against including something just because of the pleasure you had in discovering it. It is the reader's interest that you have to cultivate. Marshalling facts spread across a whole continent, blending the history of at least ten countries into a single narrative line, without losing the thread or the attention of the reader, has been a major challenge.

Mark Thwaite: Over the course of your writing have you substantially increased our knowledge of the Hundred Years War...

Jonathan Sumption: I think so. There are aspects of the war that have never been known in detail until now, because the facts are buried away in unpublished records sources. Seapower, for example, was a vital factor in the war, which has been little understood: the English could never get to grips with their enemy without being able to transport great armies with their horses and equipment by sea not just across the Channel to Calais, but as far afield as Antwerp, Bordeaux, Corunna and Lisbon. How did they do it? Why were they eventually unable to go on doing it? The activities of the irregular armies on land, operated by private captains in the English interest, are another subject on which I hope that I have cast fresh light. They played a vital part in the war. I believe that I have pieced the fragments together to provide the first coherent narrative of their deeds, and to establish how their activities were co-ordinated with those of the English governments at Westminster and Bordeaux and how the French were ultimately able to destroy them. Even where the basic facts are known, I have tried to show the connection between apparently unconnected events.

Mark Thwaite: During your researches, what discoveries about the period have most startled you?

Jonathan Sumption: One should never be too startled by anything. But small surprises are often revealing. I once read in the Public Record Office the records of an enquiry into the alleged treachery of an English garrison commander accused of taking a bribe to surrender his castle. The case ended in his acquittal. Some weeks later I found in the French archives the actual receipt he had given for the bribe. But most surprises have been of a more personal kind: a prisoner of war's correspondence with his wife, a rock hurled into the bedroom of a garrison commander where his wife was feeding their baby, a soldier's search for his lost girl-friend, a cavalryman's pet dog howling by the grave of his dead master. These tiny incidents are valuable reminders that great events are experienced by real people, of flesh and blood, whose first priority is not politics but survival.

Mark Thwaite: For you, who are the heroes and villains of the period?

Jonathan Sumption: The heroes are the rare leaders with the intelligence and perception to think outside the box, to look dispassionately at the long-term prospects of their own side. On the English side, John of Gaunt, the son of an English King and the father of another, passed much of life trying unsuccessfully to make himself King of Castile. He never occupied a throne, but became the dominant figure of the reign of his nephew Richard II. He was also the first figure of the period to be made famous by Shakespeare. Gaunt was much maligned in his own day, and is still dismissed by many as an arrogant and mediocre self-seeker. But he had a rare scepticism about what armed force could achieve and was one of the few English leaders who perceived that England could never win against a country with three times its wealth and population.

And on the French side? Charles V, who came to the throne in 1364 and died in 1380 at the age of only 44. Charles suffered from poor health throughout his reign, and never led his troops in battle, but like John of Gaunt possessed a rare intelligence and freedom from received opinions. He was the real architect of the French revival of the late fourteenth century. Gaunt and Charles never met, but they are known to have suspected and disliked each other from a distance.

As for the villains, in a war characterised by so much villainy, you have to be selective. But Charles the Bad, King of Navarre, a junior French prince in the middle decades of the fourteenth century, must rank high among the villains of any age: a treacherous, ruthless, manipulative power politician, whose natural response to determined opposition was murder and who came close to destroying his own country in the 1350s.

Mark Thwaite: How do you write? Longhand or on a screen? Straight off, or with lots and lots of editing?

Jonathan Sumption: On a screen. But computers are a great temptation to prolixity, because they dispense with the physical effort of endless recopying. You have to be very disciplined about cutting things out. So, yes, lots and lots of editing.

Mark Thwaite: Do you read the critics? Have you learned from their responses to your books?

Jonathan Sumption: Of course I read the critics. They have been kind about the book, and I am not completely free of vanity. But reading the critics is more than self-indulgence. I learn from the ones who know the period and those who, without necessarily being experts on the late middle ages, understand the historical process. History is, or at least ought to be, a branch of literature. The object is to give pleasure, and not just to oneself.

Mark Thwaite: What was the most difficult aspect of writing Divided Houses?

Jonathan Sumption: Undoubtedly the linguistic challenges. In the period covered by Divided Houses, the war involved just about all of western Europe and occasionally even Europe's eastern frontiers in Poland and Hungary. Writing from original sources, I have had to read in Latin, English, French, Flemish-Dutch, German, Italian, Occitan, Catalan, Spanish and Portuguese.

Mark Thwaite: How did you overcome this?

Jonathan Sumption: Persistence and dictionaries, and a certain instinct for languages. They come, with practice, but it can be a struggle. I admit to having been completely defeated by Hungarian.

Mark Thwaite: Did you have an idea in your mind of your 'ideal' reader? Did you write specifically for them?

Jonathan Sumption: Many historians dream of writing something that will satisfy several audiences at once: serious scholars of the period, as well as the interested reading public. That has certainly been my own ambition. I have never accepted that the two groups are incompatible. There is a large number of people out there who without being academics or scholars, enjoy serious history written to exacting standards of scholarship. The art is to recognise the human dimension of all great historical events, to explain why as well as what, and to write good English in a way that compels attention and makes the reader want to get to the next sentence.

Mark Thwaite: What are you working on now Jonathan?

Jonathan Sumption: Volume four. It will cover the years from 1399 to 1422, terrible years in which a mad King of France looked on vacantly as his country was torn apart by civil war, political assassination and foreign invasion, the background of the famous English victory at Agincourt in 1415. By the end, France had ceased to exist as an independent state, an event as cataclysmic in its day as the conquest of 1940.

Mark Thwaite: Do other periods interest you, or are you a dedicated fourteenth century man?

Jonathan Sumption: When I was teaching at Oxford, I had to cover a thousand years of European history from the fall of the Roman Empire to the Reformation. I would not claim to have been an authority on all of that. But it was good training. You cannot just enclose yourself in one short period. To understand the significance of events, you have to look beyond your own subject and see its place in the wider order of things. I still read, rather unsystematically, about every period of Europe's history, from ancient Greece to modern Germany. It gives me a sense of perspective, and some surprising insights into the detail. I have learned about the logistics of fourteenth century warfare by reading about the campaigns in Italy in the Second World War, about the problems of medieval seapower from the Napoleonic wars, and a great deal about humanity from the whole fund of vicarious experience which history has to offer.

Mark Thwaite: Who is your favourite writer?

Jonathan Sumption: You would get a different answer to that question every week. Recently, Flaubert. I have been reading his letters. Sticking to history, I have always admired historians with a broad chronological and geographical sweep, classically Gibbon, in modern times Steven Runciman, the historian of the crusades, and Réné Grousset, the French author of a masterpiece about the nomadic nations of the Asiatic steppe. But if I had to name one favourite book, it would be Fernand Braudel's great history of the Mediterranean in the time of Philip II, an extraordinary achievement in multinational history and disciplined writing. It is good to be reminded that French historians once had wider horizons.

Mark Thwaite: Do you have a favourite quote?

Jonathan Sumption: "How about a cup of tea?" (Anon)

Mark Thwaite: Do you have any tips for the aspiring historian?

Jonathan Sumption: Avoid biography, or at least political biography. Most people try it, not always successfully. Viewing events through the prism of a single life is fundamentally distorting, and provides too narrow a framework for any great theme. It is not even the best way of conveying the vagaries of human personality.

Mark Thwaite: Anything else you would like to say?

Jonathan Sumption: I could go on for ever.