Revealed: how story of Mafia plot to launch coup cost reporter his life

Thirty-five years on, the true story of why one of Italy's top investigative journalists was seized from his home in Palermo and murdered by the Mafia has been uncovered.

The investigation that began in 1970 has taken this long to wend its way to a conclusion because the truth was sensational, and murderously inconvenient to highly placed people who had the clout to stop it coming out.

It is a rare triumph for Italian justice that investigators in Palermo are now on the point of announcing their stunning conclusion. Mauro de Mauro, they have discovered, had stumbled on an amazing scoop. He learned that one of his childhood friends, a blue-blooded ex-Fascist called Prince Junio Valerio Borghese, was planning a coup d'etat with like-minded army officers determined to halt what they saw as Italy's drift to the left.

And De Mauro had also learned that in Sicily, where he worked for the evening paper L'Ora as well as for Reuters and the national daily Il Giorno, the "Black Prince" had enlisted the support of the Cosa Nostra. When the army officers seized key institutions in Rome, he discovered, the Mafia would follow suit in Palermo, occupying state broadcaster RAI and the prefectural headquarters.

De Mauro, 49 when he disappeared, was well aware that he had got hold of the story of a lifetime. To colleagues at L'Ora he said, "I have a scoop that is going to shake Italy." But he never got the opportunity to publish it. "He was an odd fish," says one former colleague at the paper. "He had a bump on his nose, a scar on his face, a permanent sneer that might have been a smile. The news room at L'Ora was one huge room."

L'Ora was a Communist paper, and other journalists scratched their heads about De Mauro's presence on it: he had been a supporter of Mussolini during the latter's inglorious last stand. Rumour had it that his nose had been broken by Partisans. He had moved to Sicily under an assumed name, started working for local papers, then in 1960 broke into the big time and began working for L'Ora, where he specialised in murders. He remained an enigma.

It was 9pm on the evening of 16 September 1970 and De Mauro was going home. He stopped at a bar to buy ground coffee, two packets of Nazionale cigarettes without filters and a bottle of Bourbon. Then he drove home. His daughter Franca, due to be married the next day, watched from the window of the family flat on Via delle Magnolie as he parked his BMW. She saw him get out of the car, then get into conversation with "two or three men". He then got into their car and disappeared - for ever. When he failed to return home, the family launched an appeal.

The investigators are now on the brink of publishing their findings. According to newspaper La Repubblica, they have established, on the evidence of senior Mafia turncoats, that top mob bosses, including former capo di capi Salvatore Riina, interrogated De Mauro to find out what he knew, then strangled him and buried his body at a place called Villagrazia. The corpse has never been found.

Less than three months later, on 7 December 1970, Prince Junio Valerio Borghese and a platoon of soldiers took control of the Ministry of the Interior in Rome. It was the beginning of the coup that De Mauro had learned about. But before the grand plan could be executed, Borghese was decisively blocked. At midnight, having loaded up a lorry with weapons, Borghese and his men went home.