In his heart, however, he always knew he would be a writer, and had numerous unpublishable novels of the mainstream variety under his belt before his first book, a clever Conan Doyle pastiche about Jack the Ripper called The Last Sherlock Holmes Story, saw the light of day in 1978. It received favourable reviews and attracted mail from serial killer buffs, or even, he suspects, from the killers themselves. Despite this Dibdin did not consider himself to be a crime writer, and in fact resisted the idea for a long while. Now, having been lauded as Britain’s best practitioner of the genre since P.D. James, he is more than happy to accept the pigeon-holing that goes hand in hand with such accolades.

From 1980 to 1984, Dibdin worked as an English teacher at the University of Perugia. There he wrote another oddity, A Rich Full Death, a detective story involving the poet Browning in Florence. The book was successful, but it still seemed that Dibdin was an author in search of his identity. That uncertainty was finally laid to rest on his return to England when he got to work on Ratking, a book which enables him to draw on his time in Perugia and which introduced his civilised but troubled protagonist, Police Commissioner Aurelio Zen. Ratking won the 1988 Gold Dagger award, and Michael Dibdin was made. Since then there have been three further Zen instalments, the latest being the just-released Dead Lagoon. So what’s the secret of Dibdin’s success, and who is he, this Venetian with the un-Italian name and the Maigret-like intuitive skills, a man who seems to blunder his way through cases?

Part of the answer undoubtedly lies in the exotic culture and setting of the Zen books, which is a refreshing departure from the insular and snootily class-conscious tradition of the English whodunit. This dispenses with the parochial plotlines and provides Dibdin with a wealth of raw material. In place of mouldy old mansions in the country and titled toffs we have the Villa Borghese, the Palatine, mad Roman drivers trying to kill each other around the Colosseum, villainy in the Vatican, terrorist gangs, and a political system that thrives on organised crime and rake-offs, all conducted on such a massive scale that it reaches into the very heart and soul of Italian life.

As Dibdin remarks, in England if there is a tainted official they say, rotten apple! In Italy they say, but of course! After a judge was blown up in Palermo two years ago, the so-called Mafia boss of bosses, Tonto Riina, was arrested, having been on the run for twenty years. A wave of congratulatory euphoria swept around the country, but as a Venetian friend put it to me at the time, the reason they caught Riina was that they began looking for him. It is that kind of clandestine world, a world of hidden power and secret agendas, with which Aurelio Zen has to deal. Often his own superiors are his worst enemies.

In Ratking, for instance, a wealthy industrialist named Ruggiero Miletti is kidnapped for ransom by the Red Brigades, and Zen is recalled from office duties to head the stalled investigation. His career has been hitherto nailed down following his involvement in the Aldo Moro case in 1978. Moro, an ex-Prime Minister, was also abducted by the Brigades. Zen made the mistake of undertaking his duties too zealously, with the result that one of his colleagues was murdered and Zen was transferred to clerical duties. It seems he was getting too close to actually finding Moro. The Miletti case therefore reawakens that painful time in his life, the difference being that Miletti’s two useless sons and his conniving daughter and son-in-law are the stumbling blocks on this occasion. Massive wealth is at stake – a lot more than the old man is worth alive.

The meaning of the book’s title serves as an excellent metaphor for the business at hand. When a nest of rats is forced to live in a confined space their tails actually grow together to form one solid mass of tissue, and the hideous monster thus formed is called a ratking. These ratkings learn to survive and even flourish. Automatically they respond as one to any threat, and the strength of one is the strength of all. They are not so much a creature as a condition, which makes the ratking impossible to destroy. There is no way of getting at it, even if the identity of the dominant rat in the pack is known.

In Vendetta, the sequel to Ratking, Dibdin again puts his finger on the malaise that bedevils modern Italy, one that has seen more than fifty governments come and go since the war. Matters reached such a head recently that the ratking imploded, destroying the main party and throwing up a new leader who already looks destined for a short political career – and so the cycle continues.

In this book a rich developer named Oscar Burolo is shotgunned to death along with his wife and two friends inside the stronghold of his Sardinian fortress, and the grisly event is recorded on closed-circuit video. The killer, however, is off-screen. Suspicion falls on a sleazy politician, Renato Favelloni, who acted as Burolo’s middleman in setting up government contracts in return for kickbacks.

Zen begins peeling the layers off the case, but then he is given the order to go to Sardinia under cover to frame another suspect and direct attention away from Favelloni. It’s the same old story for Zen – a fruitless investigation in which his own life is soon at risk. Sardinia, it seems, is even more barbaric and lawless than Sicily, and Dibdin misses no opportunities to highlight regional hostilities, longstanding family feuds, and brutal violence in this distant outpost where no one is brought to book because no one ever sees anything. Needless to say, the system wins again, and for his pains Favelloni is promoted to the senior ministry.

Dead Lagoon sees Zen returning to the city of his birth, Venice, for a spot of moonlighting from his usual job with the elite Criminalpol squad in Rome. To disguise the fact that he’s actually investigating the disappearance of a Yugoslav American, Durridge, he has himself assigned to look into complaints lodged by an old contessa, whom he had known well in his childhood, that she is being harassed in her own home by skeletons and ghosts.

Despite the fact that Zen’s motivation in taking on this case is linked with Tania, his love interest in Rome, and their mutual need for more money, Zen quickly becomes entangled with Cristiana, the estranged wife of the charismatic leader of a Venetian separatist group. Soon he is hanging up on Tania’s phone calls and, although well aware that the Venetian fog is a metaphor for the deceit surrounding him, he allows himself to indulge in romantic dreams that see him transferred to Venice and throwing his lot in with Cristiana.

The Venetian setting is realised in intricate detail. It is winter, rubbish litters the canals, and low tide exposes stinking mud. The city itself is dying, its population forced to the mainland because property, too expensive for locals, is being bought up by outsiders and left vacant. The separatist movement seeks to redress this problem in any way it can.

This is the world in which Zen finds himself in Dead Lagoon: politics, property, drugs, women, murder, corrupt colleagues, lost children, the past – all conspiring to create another of those situations in which Zen can only lose. In fact there is a losing streak running right though this man at both the professional and personal level. Getting on in years with a failed marriage behind him, unable to form lasting relationships with women and virtually handcuffed to his mother, he hardly seems to have evolved as a mature human being at all.

Coming from the peaceful backwater of Venice he is intelligent, distinguished-looking, a little naive perhaps, and emotionally scarred from his experiences. Dibdin admits that Zen is passive and something of a nonentity, functioning more as a window into Italian society than the detective-as-hero. Given the rising curve of his acclaim one can only conclude that he has hit upon a winning combination.