The Pope and the Sun King: Rita Monaldi and Francesco Sorti discuss their new novel

IT'S PERHAPS THE FATE OF SMALL countries that events from hundreds of years ago still carry great weight with their inhabitants. But how would we, as a small nation, react if someone challenged, in writing, any of the stories we'd always been told about our history? Would we boycott that individual's book? Would our media refuse to look into its claims?

In some ways, in spite of our fascination with our own history, it's hard to imagine that kind of over-sensitivity happening here, given how used we are to the betrayals and double-dealing that pepper our nation's history (what else could possibly be added to the story of Mary, Queen of Scots to make it even more sordid and corrupt than it already is?). But in Italy, it's been a slightly different experience for two former journalists, now historical fiction writers.

Rita Monaldi and Francesco Sorti had been working on another "story" for years, which they decided they would turn into a historical novel. What their research had uncovered had startled them, even surprised them, although when we consider the times they were researching – the late 17th century – perhaps they should have expected to uncover all sorts of dubious information.

But their historical investigations concerned a former Pope, Innocent XI. They fashioned their findings about him into a novel, and the result was: commercial and critical wipe-out. Their publisher withdrew their book, even as it was climbing the bestseller charts, and Italian newspapers refused to review it. Catholic historians condemned it and bookshops wouldn't even stock it. Now they cannot even get published in their own country – Italy will have nothing to do with them.

It seems a very extreme reaction to a work of historical fiction – yes, that's right, fiction – that's based 300 years ago. Monaldi and Sorti are a husband-and-wife team, the former an expert in the history of religions and the latter a musicologist. When we meet in Rome, I am struck by how utterly in harmony they are with each other, both intellectually as well as personally. Perhaps having their country seemingly united against them has drawn them closer together, united against forces that oppose them. But then, they tell me, as journalists often writing about corruption and the mafia, they were used to being the targets of other people's anger.

On one occasion in their past lives working for newspapers, Monaldi was almost shot, and Sorti had photographs and papers stolen from his apartment. It's perhaps not too surprising that now, with two young children to look after, they have decamped from Rome to Vienna, which they have since made their home. But their love-hate relationship with Rome will probably never be over. The book that began all the fuss was a historical novel called Imprimatur, which focused on the discoveries made by a real-life French agent working in Italy in the late 17th century, called Atto Melani.

To sum up, Monaldi and Sorti believe they found evidence to prove that the then Pope, Innocent XI, aided the accession of William of Orange to the British throne, an extraordinary thing for a Catholic leader to have done. "We believe that Innocent's hostile behaviour (to the Sun King, Louis XIV of France, who was allied to the Stuarts], was heavily influenced by his personal interest in the secret financial connection with William of Orange," they tell me, information that should interest Scots historians as much as Italian ones. There was a "secret alliance" they believe, between William of Orange's family, and Pope Innocent XI's family, the Odescalchi. They were prominent bankers to whom William of Orange owed a great deal of money.

But why should this upset everyone so? Well, when Imprimatur was published in 2002, it unfortunately coincided with the Vatican's attempts to have Pope Innocent XI canonised. "Someone in the church probably suspected us of undermining the canonisation on purpose and took their revenge," Sorti explains.

Is that why their book was withdrawn? Why was their publisher so concerned about what the Church thought of it? "It is a matter of fact that Mondadori, our former Italian publisher, whose president when Imprimatur was published was a prominent member of Opus Dei, eliminated our novel even from their catalogues. Members of Opus Dei, like the former speaker of the Holy See, are the chairmen of the literary prizes in Italy, who more and more often award books published by Mondadori."

Opus Dei? Conspiracies by the church and the literary establishment? Oh, what Dan Brown would give for such a publishing experience! But neither Monaldi nor Sorti, two intellectually gifted writers, come across as the kind of paranoid conspiracy theorists, or commercial crackpots after big cheques and a celebrity lifestyle, that doubters of their findings would probably suggest they are. They are extremely serious about what they do, as well as meticulous and devoted to their research. This is not a game to them, and their insistence on what they say is true is convincing. Most writers are passionate about their subjects, but Monaldi and Sorti go beyond passion, perhaps coming closer to obsession. While I am in Rome, we visit sites mentioned in their second book, spending time at the home of Louis XIV's great love, Maria Mancini, as well as the library which displays a bust of Atto Melani. They have even named their young son after the French agent, calling him Atto. It's clear that their lives have been changed by the writing of one book: how could they not be obsessed by it?

It's why I couldn't help wondering how this reaction to their first book had affected the writing of their second, Secretum. As the title suggests, it concerns the revelation of more secrets, once again involving the Vatican and a struggle for power. It has, they agree, affected them greatly.

"We wrote Secretum with the bitter feeling that the book will never appear in Italian, the language in which it is written," Sorti says. "We had totally erased Italy, our fatherland and the country where our novels are set, from our mind. It was quite an odd feeling, and it's still there." The controversy over Imprimatur took them completely by surprise. "At the beginning of writing, we had believed that no-one cared about a Pope of 300 years ago. Then we realised that old historical issues can suddenly become very hot, and even dangerous. When we were working as journalists, we had also written about pretty delicate things, such as the mafia, corruption in Italian politics, connections between gangsters and police etc. We thought, well, if we write a historical novel we will not harm anybody. We were completely wrong."

Needless to say, while they don't see themselves as Dan Brown-type thriller writers, their books do involve a healthy amount of poisoning, murder, threats and shadowy figures, all giving a convincing picture of a deadly and dangerous age, of the darkness that underpinned the glitter of the Baroque era. In this sequel to Imprimatur, Atto Melani is again operating on behalf of the Sun King, Louis XIV. The Pope is dying, as is Charles II of Spain: both Louis and Kaiser Leopold of Austria want Charles's throne. Who will the Vatican be backing this time?

"We don't need to invent very much," Monaldi says of their brand of historical fiction. "We remain within the extremely detailed frame of true historical facts that we reconstruct patiently during our research in the archives. We take pleasure in risks, going against the current fashion. Pseudo-historical rubbish has been dominating over the last four or five years, but we don't get scared. The success of our books in the most different countries encourages us to dare more."

Their controversial suggestion in this sequel is that Louis XIV, had he been allowed to marry his first love, Mancini, would probably have been a better king than he was, ruling more fairly and pursuing a less aggressive foreign policy.

And perhaps, who knows, even altering the path of the French monarchy that led, fatally, to the revolution just 80 years later. It seems hard to believe, at first, that a king's choice of wife should affect the future of an entire country – then I remember Henry VIII, Anne Boleyn and the break from the Catholic Church.

I ask Monaldi and Sorti if this means their books are essentially about the power of an individual. No, they assure me. "That would be a mistake. Power is essentially an illusion." At the moment, it's just such an illusion that's being exercised by a publishing industry in their native country, keeping them out of the bookshops there. Hopefully, though, not for much longer.

• Secretum is published by Polygon priced 16.99