Forty-three years ago this week, the BBC reported on the death of Roberto Calvi, an Italian banker whose body was found in strange circumstances in the centre of London. His bank was linked to the Vatican, a masonic group and the Mafia – and his murder left many unanswered questions.

Roberto Calvi was the chairman of the prestigious Banco Ambrosiano, the largest private bank in Italy. He was so closely connected to the Roman Catholic Church that he was known as "God's Banker".

Warning: This article contains references to suicide and murder

But in June 1982, the 62-year-old Calvi went missing. And on the morning of 18 June, his body was discovered hanging beneath Blackfriars Bridge in London.

"Calvi was at the centre of an incredibly complex web of international fraud and intrigue," reported the BBC's Hugh Scully. "It involved the Italian banking world, the underworld, the Mafia, Freemasonry and, most startling of all, the Vatican." The banker's death would trigger a wide-ranging political and financial scandal in Italy. It would involve the disappearance of millions of dollars, and leave behind an enduring mystery.

Calvi had been missing for nine days before he was discovered hanging from scaffolding beneath the bridge. But it was the strange circumstances of his death that puzzled UK police. His pockets were stuffed with bricks, and with some £10,000 ($14,000) in cash in multiple currencies. He also had a fake passport bearing the name Gian Roberto Calvini. Despite this, the initial coroner's report in July 1982 found no evidence of foul play on his body, so ruled that the banker had taken his own life. But even at the time there was suspicion that something far darker was afoot.

"Calvi's last journey was hardly that of a man contemplating suicide," said Scully. "Indeed, he had made the most elaborate plans to get out of Italy secretly." The banker had shaved off his moustache to avoid being recognised before disguising his route out of Italy by going through other countries first and hiring a private plane to spirit him to London. "He had taken a one-month lease on a flat in Chelsea and then there was a false passport and an airline ticket," Scully continued. "Inside the passport was a current visa for Brazil and the airline ticket was for a one-way ticket to Rio de Janeiro. Why, you might ask, go to all those lengths simply to finish up on the end of a rope under Blackfriars Bridge?"

Calvi's was not the only unexpected death at Banco Ambrosiano. The day before his body was found, his personal secretary Teresa Corrocher had also apparently jumped to her death from the fourth floor of the bank's headquarters in Milan. She left behind a note condemning her boss, writing that he should be "twice cursed for the damage he caused to the bank and all its employees".

Calvi and his bank had operated in a murky world where finance, organised crime, politics and religion overlapped. Founded in 1896, Banco Ambrosiano had a long history with the Catholic Church – and the Institute for Religious Works (IOR), often known as the Vatican bank, had become its main shareholder. IOR holds the bank accounts of the Pope and the clergy, but it also manages the church's financial investments. Because the Vatican is its own country, Italian regulators have no control or oversight of the IOR.

"The Vatican is entirely free of exchange controls and other government regulations; secrecy is everything," said Scully. "The Vatican has to account to no one for its financial dealings, and enormous sums of money can be sent anywhere in the world without anyone knowing about it........

© BBC