The Most Reverend Paul Marcinkus, who was found dead at his home in Arizona on Monday evening, caused enormous harm to the reputation of the Catholic Church through his stewardship of the Vatican bank, which he headed for 18 years. He was 84.

Nicknamed “the Gorilla,” the burly American prelate was best known for his involvement in the Banco Ambrosiano scandal, a banking crash that cost the Vatican about $500 million and did untold damage to its prestige. The chairman of Ambrosiano, Roberto Calvi, was found hanging under Blackfriars Bridge in London in June 1982, shortly before Italy’s largest private bank went bust with debts of $1.3 billion. Embarrassingly for Marcinkus, the pope’s bank, the Institute for Religious Works, had been an active partner in Calvi’s hazardous financial adventures.

The fallout from the scandal lasted for more than a decade. In 1984 the Vatican agreed to make a $240 million goodwill payment to creditors of the Banco Ambrosiano, while denying any responsibility for the fraudulent collapse of the Milan-based bank. The payment failed to mollify the Milan magistrates investigating the case, who issued a warrant for Marcinkus’s arrest in 1987.

This decision was followed by a protracted dispute between the Vatican and Italian judicial authorities, which resulted in Marcinkus and two of his aides at the bank spending long periods holed up in the Vatican for fear of arrest if they set foot on Italian territory. The case eventually was dropped, but the attempt to arrest Marcinkus for alleged complicity in fraudulent bankruptcy came as a severe shock to millions of Catholics around the world.

Paul Casimir Marcinkus was born in Cicero, Illinois, on January 15, 1922. The son of a Lithuanian immigrant who worked as a window cleaner, he was ordained as a priest in 1947. Having worked briefly as a curate in a Chicago parish, he moved to Rome in 1950 to study canon law. A temporary job at the Vatican Secretariat of State turned into a permanent job and enabled him to make friends with Giovanni Battista Montini, the future Pope Paul VI.

After overseas assignments in Bolivia and Ottawa, he returned to the Secretariat of State in 1959 to begin a 30-year stint in the central government of the church, which led to his becoming secretary of the Institute for Religious Works in 1969 and president of the bank in 1971 – this despite the fact that he had no previous banking or business experience. It was a time when Pope Paul VI was in dispute with Italian authorities over Vatican taxes and anxious to begin shifting Vatican investments out of the Italian market and into foreign holdings.

Thus Marcinkus – who once said, “My only previous financial experience was handling the Sunday collection” – became involved in years of controversy over the baffling international complexities of the Ambrosiano affair and over the dispute about whether he had sold a major shareholding of Banca Cattolica de Veneto to Roberto Calvi.

He remained head of the Vatican bank despite rumors that John Paul I, in his 33-day pontificate, was trying to get rid of him, continued in the post under John Paul II, and was appointed titular Archbishop of Orta in 1981. But he became virtually a prisoner in the Vatican himself after the Ambrosiano scandal exploded in 1982, and thereafter did not accompany the pope on foreign trips.

Standing 6 feet 4 inches and a lifelong sportsman with a particular predilection for tennis and golf, Marcinkus became an unofficial papal bodyguard and was among those responsible for saving Pope Paul VI’s life when a deranged Bolivian painter lunged at him with a knife during a visit to the Philippines in 1970. He was also a close friend of the pope’s influential secretary, Monsignor Pasquale Macchi.

If these friendships helped to promote his ecclesiastical career, which culminated in his being made acting governor of the Vatican City State, other, more controversial friendships ended by denying him the cardinal’s red hat that otherwise would have been his by right.

The first was that with Michele Sindona, the Sicilian financier who committed suicide in an Italian jail in 1986 after being convicted of commissioning the murder of the Italian official who had been investigating his affairs. Sindona had been convicted previously in America for his role in the collapse of the Franklin National Bank.

But Marcinkus’s most damaging association was that with Roberto Calvi. Like Sindona, Calvi was a member of the sinister P2 masonic lodge, so hardly a suitable business partner for a senior church official.

Marcinkus used to acknowledge that “you can’t run the church on Hail Marys,” but his excessive pragmatism ended up doing both moral and financial harm to the church.

In 1990 he left the Vatican for Chicago, then went to work as an assistant parish priest in Sun City, Ariz. He lived in a white cinderblock house on the edge of a golf course and was popular with his parishioners.

Marcinkus was portrayed by Rutger Hauer in the Italian film “Il Banchieri Di Dio” (2002).

Four people are currently on trial in Italy charged with murdering Roberto Calvi; there was speculation that the accused might attempt to call Marcinkus as a witness, although his diplomatic status would have made this difficult.

Despite the efforts of prosecutors in several countries, Marcinkus was never questioned about claims of money laundering, shell companies, the collapse of the Vatican bank, or the death of Calvi.

Some even implicated Marcinkus in the supposed murder of Pope John Paul I, who died a month after his election in 1978.The motive for murder was allegedly the pope’s determination to clean up the Vatican’s finances.

According to David Yallop, whose book “In God’s Name” (1984) articulated the theory of John Paul I’s “murder”: “Marcinkus is a crook, a criminal, a man who in the normal world would have served a long prison sentence for his part in a whole array of financial crimes.”

Marcinkus always denied any wrongdoing. On his departure from Rome, he had provided journalists with his own candid epitaph: “I have no doubt that I will be remembered as the villain in the Calvi affair.”

To what extent he was villain or dupe remains unclear; he himself was never willing to assist those who attempted to shed light on the issue.