During my last trip to Portugal I told myself that I wouldn’t buy any books. Like many booklovers, I’m a compulsive buyer of books. In the past I’ve skipped buying certain food items to have the money to buy books (a habit that my family challenged me over years ago when they saw how thin I was getting. I tried to argue my intellect and inner world were growing even as I was getting physically thinner, but I eventually saw their point of view).

This time my resolve not to buy books was practical. I had travelled with only a small rucksack and there was no space to bring anything home. However, when I saw a copy of O Mistério da Estrada de Sintra (The Mystery of Sintra Street), I couldn’t resist. This is thought to be the first Portuguese detective story. It was published in 1870 in serial form in the newspaper Journal de Notícias. Its co-author, Eça de Queiroz, is one of the great figures of Portuguese letters, a nineteenth-century novelist who wrote prolifically and spent many years outside of Portugal in his role as a diplomat (including in Newcastle-Upon-Tyne, where there is a plaque on the house where he lived).

In the preface to the book, which Queiroz co-wrote with literary friend Ramalho Ortigão, the authors say that each of them began the book with “a ream of paper, joy and audacity.” As I write my own Portuguese-set detective novels, I can’t help but take inspiration from their motives. I can’t think of many better things for a writer to have: blank paper, joy, and audacity.

Queiroz was well aware of contemporary literary trends across Europe, especially in England and France. He would have known the impact that writers like Wilkie Collins and Elizabeth Braddon were having in England with The Woman in White and Lady Audley’s Secret. Dickens’ books were becoming more sensational, relying on twists and turns of plot. The Mystery of Sintra Street would have fitted well alongside these books.

One mystery that I’ve been trying to solve myself is why this book, the first Portuguese detective story, wasn’t the start of a wave of popular crime fiction in Portugal. In Britain we had the Golden Age of crime fiction in the twentieth century, with popular writers like Christie, Allingham and Sayers becoming household names.

While Penguin books were publishing affordable books for ordinary people during the interwar years, I suspect Salazar’s fascist Estado Novo would have discouraged the democratization of reading. The culture of ‘Fátima, Fado and Football’ meant that ordinary people were given Catholicism, music and football, which the state hoped would keep them compliant and quiet. In this context a popular reading movement wouldn’t have been welcome. I’m speculating a little on this point, so would happily defer to the views of experts in Portuguese literature and culture.

Perhaps the most intriguing mystery of Sintra Street is why it wasn’t the start of a movement in Portuguese detective fiction…