One summer, with my wife Roz and our three sons, I visited the Château du Clos Lucé in the French city of Amboise, where Leonardo da Vinci spent his last years. The château is now a museum dedicated to Leonardo, with working models of many of his inventions. On that summer’s day a seed was planted in my mind, to write a novel that somehow involved Leonardo’s work. But life and other novels intervened, and the idea just got filed away. Then one day, years later, Roz said: ‘You should go back to Leonardo.’ So I did. And the result is The Leonardo Gulag.