Several of our walks of London cross over Blackfriars Bridge. But what few people who do so realise is that the bridge was central to one of the great mysteries of the 1980’s, the death of the man who was known as God’s banker, Roberta Calvi.

It was under Blackfriars Bridge on 18th June 1982 that the body of the missing Italian banker, Roberto Calvi, was found  hanging with a length of orange rope woven into a lover’s knot around his neck. He was weighed down by bricks and found with $15,000 in cash in his pockets.

Nine days earlier, the man known as “God’s Banker” for his links with the Vatican, had fled Italy, altered his appearance to avoid detection and, via several clandestine trips around European capitals, made a final, fatal, trip to London.

The motive for what, until recently, was treated as his suicide seemed crystal clear Calvi, the former chairman of the disgraced Banco Ambrosiano, Italy’s largest bank, was up to his neck in financial scandal.

The week following his death he was due to appear in an Italian court of appeal, having previously been sentenced to four years’ imprisonment after several billion lire were illegally exported from the bank, then on the verge of collapse. A further trial for alleged fraud awaited him.

But his death, and the London coroner’s report which concluded that it was suicide, were only the beginning of a 21 year mystery which continues to this day.

In 2002 forensic scientists concluded that the banker did not take his own life but was murdered. However, despite the intense level of interest in the tale, which puts Calvi at the centre of a dark riddle involving the Mafia, the Vatican and an ultra-powerful Catholic Masonic Order known as P2, it has never been solved.

The latest twist in the tale came when Italian prosecutors finally concluded that the Mafia ordered Calvi’s murder and named four people suspected of carrying out the killing.

On March 2005 Flavio Carboni, a Sardinian businessman, and Pippo “The cashier” Calo, a leading figure in the Sicilian Mafia,  who is currently serving a life sentence for a 1984 train bombing that killed 16 passengers, went on trial  in a Rome courtroom charged with conspiring to lure Calvi to London.

On trail with them were Ernesto Diotallevi, a senior figure in Rome’s underworld, and  Manuela Kleinszig, an Austrian who at the time of Calvi’s death was a girlfriend of Carboni. All deny any wrongdoing.

According to the latest reconstruction of his final hours, Calvi met his killers at the flat in Chelsea at around 10pm on June 17th. Although Calvi often travelled with a retinue of around a dozen bodyguards it is appears that he made the fatal mistake of trusting his visitors and of being alone in their company. He was taken to the Thames. Bruising on his arms and right wrist together with marks on the soles of his shoes suggest that he struggled with his assassins when they attacked him either on the river bank or on a boat as it approached Blackfriar’s bridge. Next they either drugged him or applied a slow and steady pressure to his neck, almost strangling him. They then stuffed bricks into his pockets and down the front of his trousers together with $15,000 in cash. A noose was then placed around his neck and the orange rope was tied to a ring on scaffolding under the bridge. Calvi was probably still alive - although unconscious - as the boat was moved away and the weight of his body and the bricks combined with the river’s current, slowly tightened the noose. It has been estimated that he could have taken anything from 30 to 60 minutes to die.

A panel of forensic experts concluded that Calvi, whose body was exhumed in 1998, could not have committed suicide - not least because he had been strangled before the cord was passed around his neck. Their report also said that his hands had not been in contact with the seven bricks found in his pockets and the waistband of his trousers that he supposedly used to weight his body. The tribunal concluded he had been murdered and then hanged to make it appear like suicide.

Calvi’s son, Carlo, claims that the Mafia did not act alone and claims that his father was eliminated by politicians because his position had become untenable. He was going to have to defend himself against and reveal the activities of the Institute for Religious Works  - better known as the Vatican bank. He also claims that the mafia’s aim in killing Calvi was not only to punish him for his misuse of its funds, but also to prevent him from blackmailing Politicians, the clandestine P2 Masonic group and the powerful Vatican bank itself.

Whatever the fate that befell Roberto Calvi, his death is most certainly one of the Thames’s most baffling recent whodunits and the involvement of the Vatican one of its most intriguing aspects.