By Angelo Amante and Wladimir Pantaleone
PALERMO, Italy (Reuters) - When Salvatore Catalano discovered that mafia boss Matteo Messina Denaro had lived just a short walk from his house in the western Sicilian town of Campobello di Mazara, he felt sick.
Catalano's brother, Agostino, was a policeman who died in a 1992 bomb that killed anti-mob magistrate Paolo Borsellino - a attack that prosecutors say Messina Denaro helped mastermind.
"There's anger in my heart and soul now that I know he was here and I didn't recognise him," Catalano told Reuters.
Messina Denaro, 60, was arrested on Jan. 16 after 30 years on the run. Police believe he spent much of the last year hiding in plain sight in Campobello di Mazara, a town of some 11,000 inhabitants, just a short drive from his mother's house.
"We've celebrated the arrest with my family. He's in jail and will now be subject to tough detention rules," Catalano said.
The last confirmed sighting of Messina Denaro was in 1993, making it difficult for police to identify the most wanted man in Italy. He lead an apparently open life in the town, shopping for himself in the local supermarket, authorities said.
Prosecutors say their hunt was further complicated by the unusually strong loyalty he received from members of his clan in the west of Sicily.
Reuters interviewed dozens of residents on the streets of Campobello and from his nearby hometown of Castelvetrano, as well as prosecutors and police who helped track him down.
They revealed the struggle investigators faced in trying to break through the mafia's wall of "omerta", or code of silence, that had shattered in other parts of Sicily, but which still stood firm around Messina Denaro, dubbed by the Italian press as "the last Godfather".
"I've arrested at least 200 people related to him. Only one of them decided to collaborate with justice," said Roberto Piscitello, a prosecutor who tried to capture Messina Denaro from 1996 to 2008.
"In the nearby provinces of Palermo and Agrigento, five out of 10 of the arrested become turncoats," he told Reuters speaking from his home in Marsala, on the western tip of Sicily.
In the end, it wasn't Messina Denaro's fellow mobsters who betrayed him, but his failing body.
Police say they managed to catch Messina Denaro after learning from wiretaps of his relatives that he had cancer.
They had long suspected he was living in his native Sicily, and a thorough check of cancer patients in the region revealed that a man named Andrea Bonafede had surgery in the western city of Mazara del Vallo at the same time his mobile phone had been active in another part of the island.
Investigators took that as the "first significant confirmation" that Messina Denaro could be hidden under that false identity, judicial documents seen by Reuters showed, because it suggested the man having the operation was not the real Andrea Bonafede, who was presumed to be with his phone.
They homed in on the patient and learned he was due to receive routine chemotherapy treatment in the island's capital Palermo on Jan. 16.
Police surrounded the clinic and pounced after the patient arrived for his appointment. He immediately acknowledged his true identity but appeared to dash any hopes that he would spill the beans on his life of crime.
"I have my code of honour," a law enforcement source quoted him as telling magistrates when they first met him, referring to the Sicilian Mafia's rule, much degraded over the past 30 years, of not speaking about the organisation to anyone outside.
His silence means investigators must try to piece together as best as they can how he managed to avoid detection through the years.
The initial focus of their probe was on the real Andrea Bonafede, a trained surveyor who had no criminal record.
Bonafede has confirmed knowing Messina Denaro since their youth and has acknowledged buying the mobster a flat in Campobello di Mazara, prosecutors said. He himself is under arrest and has not commented publicly about the case.
Police are also investigating his driver, Giovanni Luppino, an olive farmer who also had no police record. He was carrying a switchblade and had turned off his two mobile phones, in what magistrates say was an attempt to prevent being traced.
He has denied knowing the true identity of his passenger.
Palermo Chief Prosecutor Maurizio de Lucia told Reuters that men such as Bonafede represented the "first link" of the fugitive's matrix - those who provided for his basic needs.
But he believes his support network had deep roots.
"His territory helped him for many years. It is reasonable to think he received protection from professionals, entrepreneurs," he said.
Among those already under investigation for allegedly aiding and abetting the boss is his doctor, Alfonso Tumbarello. His lawyer said he was confident his client could prove his innocence.
Magistrates said they found evidence that Messina Denaro had visited Spain, Greece and Austria over the years. But the main focus of his business activities remained in western Sicily, meaning he probably spent much of his time on the island.
Dozens of lower-level mafiosi were arrested in the region through the years - a thinning out of Messina Denaro's inner circle that magistrates said repeatedly interrupted promising leads that they had hoped would one day take them to the boss.
"(But) we could not sacrifice justice. We could not leave mobsters on the streets," Prosecutor Paolo Guido, who led the long hunt to the boss in the last years, told Reuters.
Prosecutors said the mob chief built a wide array of financial interests that went far beyond traditional mafioso concerns, helping him set up a loyal network of white collar professionals.
A secret 2013 recording made in prison revealed former boss of bosses, Salvatore "the Beast" Riina, had complained that his one-time protege was investing in renewable energy projects rather than focusing on hardcore Mafia activities.
"In the Sicilian context, those who are believed to create jobs and the possibility of doing business obtain consensus, protection," said Colonel Antonello Parasiliti Molica, who heads the Carabinieri special forces anti-crime unit in Palermo.
(Writing by Angelo Amante; Editing by Crispian Balmer and Ross Colvin)