If you go to the Campo dei Fiori in Rome, you’ll see in the centre a large bronze statue of a man, his face shadowed by a monk’s cowl, glowering over the market stalls below. If you were to go on the 17th February, you would see a procession of contemporary pilgrims leaving poems and flowers at his feet, all around the plinth. They regard him as a hero, a champion of free speech and a defiant icon of progressive, scientific thought, but in reality he was more complicated than that.

I’ve been living with Giordano Bruno for twenty years now and I find him more intriguing as time goes on. I first discovered him as a student when I became interested in the history of occult thought in Renaissance Europe, and fell in love with his story immediately. I was fascinated by this rogue Italian philosopher who started out as a Dominican friar in Naples, but fled his order to escape the Inquisition, went on the run through Italy, found work as an itinerant teacher and within three years had ended up in Paris as personal tutor to the King of France. I was curious about the years he spent in England, where he became the friend of poets and courtiers. I wondered what kind of man he must have been, to have chosen to live his life in exile in return for the freedom to write his books, filled with ideas that could get you into serious trouble in conservative Christian Europe in the sixteenth century.

I loved the many contradictions he seemed to embrace: his scientific theories (he was one of the first people to argue that the universe was infinite, at a time when even the ideas of Copernicus were still frowned upon) stood alongside a fascination with magic and ancient religions. He managed to get himself imprisoned for heresy by both the Catholics and the Protestants. He was, by all accounts, a brilliant public speaker and the kind of guest everyone wanted at their dinner table, but equally quick to offend people he disagreed with; he became a friend of kings and nobles, but spent most of his life on the move, never quite finding a reliable patron or a place to settle.

From my first encounter with him, I wanted to tell his story, but I couldn’t find the right way into it. I put him to the back of my mind and wrote other books, but I couldn’t forget him, and a few years ago I came across a book that suggested he had worked as a spy for Queen Elizabeth’s government while living in England. The whole rich history of early espionage opened up and I knew I’d found the key to writing about him. Two of my enduring literary passions since childhood have been history and detective novels; I wanted to put Bruno, with all his rich complexities, into a murder mystery that would also try to capture the turbulence of the late sixteenth century. This is where the series began. My version of Bruno is a fictional creation, though many of the situations he encounters are based on historical fact. But I hope he possesses the defiant courage, wit and infuriating stubbornness of the original. He continues to fascinate me; I hope you’ll be intrigued by his adventures too.