Cast Iron: Peter May on Researching the Final Enzo

As always, the final Enzo book took me on yet another tour of France that was well off the beaten tourist track.

The most unusual location was the Lannemezan high security prison which nestles in the lee of the Pyrenees, a stone's throw from the Spanish frontier. I am not new to French prisons, having visited several around the country to talk to inmates. But Lannemezan was my first high security stop - a prison which harbours some of France's most notorious and violent murderers. These include the infamous Patrice Alègre, who provided the inspiration for the serial killer in Cast Iron.

I didn't meet Alègre, and had no desire to - I don't believe we should encourage such people to believe that they are celebrities. But the prison itself is a formidable place that sits squarely between two railway lines just outside the country town of Lannemezan. The greatest irony of the place, it seemed to me, was that from the windows of their cells many of the inmates had a clear view of the mountains which had provided the escape route for many fleeing the Nazis during the Second World War - a route to freedom seen from a place of incarceration.

But while Alègre provided the inspiration for my killer, I based him physically on a notorious British criminal of the sixties and seventies, the armed robber John McVicar who was declared Public Enemy No.1 by Scotland Yard after several prison escapes. I interviewed McVicar in the late seventies after he had been paroled and become a journalist and media commentator. I visited him at his mother's house, where I was struck by his extraordinary presence. The interview was part of the research for a book which I never wrote, but I was happy to recall and make use of the encounter many years later, and imbue the character in Cast Iron with at least some of McVicar's extraordinary characteristics.

My researches also took me to Bordeaux in the west of France. This was a research trip of some contrasts, leading me to the ultra modern Palais de Justice during the day, and the bars and dark and seedy streets of the city's red light district at night - providing me with insights into the city which I had never had on previous trips.

I then went east to a château and estate owned by friends near the town of Duras. This became the model for the home of the parents of the murdered girl in the book. In my story, the bones of Lucie x had been found in the milky green waters of the fictitious estate's dried up lake during the heatwave that seared the French countryside in 2003, and using my friends' estate as the location enabled me, I hope, to imbue the writing with a real sense of place. I was also able to borrow much of the history of the actual place to embed the fictitious one in the very dramatic history of the area during the Plague and the Hundred Years War, when almost the entire population had been wiped out, and the area was dubbed "The Desert Lands".

Not far away, I did a solitary tour of the very grand and labyrinthine Château Duras to provide myself with essential detail for a typical Enzo escapade, combining both fear and humour in the way that only Enzo can.

Another essential location for Cast Iron is to be found in a large country house near Biarritz in the extreme south-west of France. For this I went to stay at the Hotel Château du Clair de Lune which provided the perfect setting. The hotel is in a 19th century manor house of extraordinary design, with sweeping red tiled roofs that raise themselves like eyebrows over its many dormer windows. It sits in eight hectares of lush parkland, rich with magnolia and rhododendron, and provided the perfect location for the dénouement of my story.

Last but not least was the invaluable advice I always receive from my long-time pathology and forensics advisor, Dr. Steve Campman. I was first introduced to Steve many years ago by the late Dr. Hibbard Williams, former dean of the University of California Davis Medical School. Steve was then working as a young intern at the Medical Examiner's office in Sacramento. He provided me with invaluable detail on several autopsies I was writing for the first of my China Thrillers, The Firemaker. We had corresponded only by email, and I had asked him for advice on a particularly unpleasant autopsy on a burned body. Imagine my surprise when I got up the next morning to find that the fax machine in my study had spewed out rolls and rolls of paper during the night, providing me with more than eighty pages detailing the autopsy I would go on to write. Steve had taken his pages of notes to his local Kinkos, a document printing and copying store near his home, to have them faxed. The cost, he had been told, would be three dollars. He wasn't earning much at the time and figured this was a bargain, since he didn't have a fax machine of his own. It was only after the fax had been sent that he realised that it was three dollars per page.

I didn't learn this until many years later, since then I have plied him with champagne and gourmet meals to try to appease the terrible guilt I felt.

Steve is now the Medical Examiner in San Diego. Over the years he and I have become firm friends, visiting each other at our respective homes in France and the US, and he has provided all the forensic and pathology requirements for the entire Enzo series - as well as many of my other books.