He fled Italy after one of the country's largest private banks, Banco Ambrosiano, went bankrupt under his chairmanship with debts (according to various sources) of between 700 million and 1.5 billion dollars. Much of the money had been siphoned off via the Vatican Bank, the Istituto per le Opere Religiose or IOR, the 'Institute of Religious Works'.
His body was found hanging beneath Blackfriars Bridge (itself a masonically significant location) in June 1982. Coincidentally, Calvi was in fact an adherent of Licio Gelli's secret masonic lodge, P2. Curiously, the British police treated Calvi's death as suicide, despite all evidence to the contrary. An enquiry (following Calvi's exhumation) in 1992 confirmed the murder.
In 1997, Rome prosecutors implicated a member of the Sicilian Mafia, Pippo Calò, in Calvi's murder, along with Flavio Carboni, a businessman with activities in really many fields. Two other men, Ernesto Diotallevi (supposedly, leader of the "Banda della Magliana", the most dangerous Roman mafia-like association) and Mafia banker Francesco Di Carlo are also alleged to be involved in the killing.