For six years, he is sheltered, fed and educated by political activists before giving himself up back in Italy. He is beaten, tortured and spends the next seven years in prison, mostly in maximum security in Milan, Turin and Padova, with some of the country's most hardened criminals.

His battle with the courts becomes one of the most famous cases in Italian law: 80 judges and magistrates are involved; he is tried and retried 11 times; the case drags on for 18 years; his legal paperwork weighs 96 kilos. Eventually, after an international campaign, a Scotland Yard expert says the forensic procedures used in the case are 20 years out of date and the President of Italy pardons him.

Two of his books are made into films, and a third, The Dark Immensity of Death, produced by Aurelio De Laurentiis, is on the way. He has a huge following in Italy and France and is about to test the British market. He now lives in Quartu Sant'Elena, just outside Cagliari, in Sardinia with his wife, Colomba, and two-year-old son Giovanni. 'I'll make sure I send him to the scouts,' he says, laughing.

You couldn't make it up. You wouldn't have to because that, in brief, is the life story of Massimo Carlotto.

We meet in a gastropub in east London. I'm expecting someone weighed down by his troubled past, but Carlotto proves an engaging conversationalist with a penchant for self-deprecation. Rugged, stubbly (he has lots of female fans), he is simply dressed in dark clothes. Now 48, he has the impressive physique of an ex-rugby player (and he probably weighs a few kilos more than his legal history).

Judging by the detailed description of what Alligator and his friends eat between stake-outs - pappardelle with chicken livers and a suitable vintage, baccala, an elaborate pumpkin risotto - one would assume that Carlotto missed a decent meal while in prison.

'Not at all,' he says, lighting up the first of a series of black cigars. 'I was in with the right people, mafiosi who, because of their connections, were able to buy privileges. They could get decent produce, so they spent a great deal of time planning a menu and cooking. To put it succinctly, you could say I ate a lot of very lavish Sicilian and Calabrian meals.'

Carlotto made good use of his time inside. He was a negotiator between rival factions, made valuable friends from the world of organised crime as a 'scribe', writing letters and documents for fellow prisoners. And now he uses those contacts from the criminal world to add more than a touch of reality to some of the most hardcore material on the crime shelves. A leading member of the 'Mediterranean Noir' group who lament the lack of investigative journalism in Italy and, to a lesser extent, France and Spain, Carlotto says his novels are all based on real criminals, real killings, real life. His graphic descriptions of gruesome deaths - from a straightforward shooting and throat-slitting to an arranged car crash, an impaling on a lance and murder by fist-fucking - offer an insight into the company Carlotto keeps, or kept, the friends he made 'inside'.

'I have never once made up a killing,' he says. 'Every single death in everything I have written relates to a real killing, one for which I have read the autopsy report. I have seen the documents, I have carried out one-to-one interviews with murderers. This is my way of recording what is happening in present day Italy.

'The Noir writers talk about the social and political situation right now; they react very quickly to changes in the criminal world. In Italy, Mediterranean Noir is called the literature of reality. I even have journalists calling me when they are writing about crime, to ask me what is going on. The world of journalism has changed. There is no investigation now. Italy has lost any real sense of truth, because nobody believes the official "truths".

'It is very rare now for crime writers [in Italy] to invent stories. Most of them are real. Only the names are changed. That's why these books are so popular.'

Carlotto reckons there are about a dozen writers in the Mediterranean Noir movement. Two of them have died in the past four years but their work is published in English - Jean-Claude Izzo, a French-Italian whom Carlotto rates best of all, and the Catalan Manuel Vázquez Montalbán. If Carlotto sells well in translation, then more Noir writers will be translated. The most popular is Andrea Camilleri, the Sicilian whose books sell 200,000-300,000 in Italy; Carlotto's sales figures are not far behind.

Imprisoned crime writers are not rare in Latin America, where Carlotto has family and many friends. The biggest name in English-language crime writing who spent years behind bars is Edward Bunker, the American who was in prison for around 30 years in various institutions for a series of crimes he did commit. Carlotto has never met Bunker but has read all his works and is a fan.

Whether 'reality crime' from the Mediterranean will prove popular in the English-speaking world should become clear this year, with a second Carlotto book about to be published. Since Henning Mankell won the Gold Dagger, the top crime award in British publishing, in 2001, there has been a Euro-boom. Maxim Jakubowski, author, critic, and owner of Murder One, the London specialist bookstore, reckons sales of translated works have gone up five-fold in recent years. The cultural differences - not least language - the sense of place, the strengths and weaknesses of a variety of investigating agencies, and the depth of character in many works can make Euro-crime far more rewarding than, for example, mainstream American books.

The Colombian Mule, Carlotto's 2001 novel about drug smuggling and police vengeance, was published in the UK last year. The second, The Master of Knots, is set against a backdrop of police brutality at the anti-capitalist demonstrations at the G8 summit in Genoa in 2001 and explores the darkest depths of S and M, disappearing parents, snuff movies and prostitution. It is based on a real case, the details of which were sent to Carlotto by a reader's email that started: 'Dear Alligator.'

Carlotto accepts that his own leading characters are far from pleasant. Is it really so grim underneath the surface of life in modern Italy? 'Yes, but you have to bear in mind that things have changed. Alongside the changes in the global economy there has been a revolution in the criminal world, too.' According to a United Nations report five years ago, he says, the worldwide annual income from organised crime is measured in thousands of billions of dollars, and the biggest problem for criminals is laundering the money.

'The most popular area for recycling it is the Mediterranean because of the well-developed relationship between the various mafias and banking, industry and politics. In the richest part of Italy, the north east, there is very close interweaving between the legal economy and the black economy. The very top levels of the underworld have realised that they have to infiltrate the productive manufacturing process. They have to work with others, and the balance between different mafia organisations has changed, producing different strata, different cultural layers.

'While the Sicilian mafia has retracted to the south, the Nigerians have become heavily involved in drugs, the Romanians run prostitution, the Chinese and Croatians have their sweatshops and at a lower level you have the Albanians. There is acompletely new situation regarding organised crime.'

There are new rules, too. The old-style mafia 'code of honour' - never grass, never steal a friend's girl and so on - no longer applies, he says. And he should know, since his best source of information is an old-style mafia man. Other sources include lawyers, readers, the majority of whom, he says, are women, and, occasionally, police officers.

There are three main characters in the Alligator series. The 'brains' is a computers and information geek who drinks too much, cooks sumptuous meals, rarely goes out and holds extreme left-wing views. The muscle is provided by Rossini, based on Carlotto's real-life top criminal source, who never shirks from a cold-blooded execution. Then there's the Alligator himself: nightclub owner, blues and jazz fan, always in search of 'the truth'.

'I develop the plots out of actual legal cases, legal errors,' says Carlotto, sipping an espresso. 'The Alligator is a kind of loser who uses his skills in the service of other losers.'

What about the casual way in which the perceived 'good guys' will execute opponents? 'I'm not interested in the good guys winning and the bad guys losing,' he says. 'There's innocence and innocence ... I'm interested in reality, and this is real.'

Even down to the choice of car. Not many hard-nuts would be seen behind the wheel of a Skoda, but the Alligator drives one - and Carlotto did, too 'but my wife won't let me now, so it's a Citroën' - because the Skoda is the car least stopped by police on Italy's roads.

His wife is an accountant in the local tax office and he is just about to open a bookshop in Quartu because there isn't one and will be running writing courses from the shop. His only weakness seems to be a passion for calvados. 'Everyone knows about whisky, grappa, no one knows about calvados.' He drinks a cocktail named the Alligator, after his character, invented by a barman in Cagliari - three parts Drambuie, seven parts calvados, served with lots of crushed ice and a slice of green apple 'to eat and console yourself when the glass is empty'. 'Nobody can drink more than four, and nobody ever has.' The fame of this cocktail has spread and you can now get an Alligator at bars in Rome, Milan and Naples.

The conversation turns serious. Did Carlotto ever give up hope during those lost years, most of them spent in maximum security, thinking: 'I'll be an old man before I'm out. I'm in here for life'?

'Twenty-four hours a day,' he says.

Whom does he hold responsible for the loss of so much life: a corrupt policeman, a political opponent, a judge? 'Il sistema,' he says. The legal system that he, and his supporters, helped to change. It still has its faults. In the 1980s, Cesare Battisti, another Italian writer, was sentenced to life imprisonment for terrorism, in absentia, under special laws. He has always pleaded innocence but is now himself a fugitive because the French government has agreed to an extradition request from Italy. Carlotto is among those campaigning for Battisti's freedom.

Many of Carlotto's generation were wrongly imprisoned, he says, always because of their politics. Carlotto would have been cleared immediately had a proper forensic investigation taken place in 1976. He is still waiting. A hair from under the victim's fingernails, which would have given a DNA sample, mysteriously 'disappeared' from a safe at the coroner's office. This is one case even the Alligator could not solve.