Police in the City of London have re-opened inquiries into the death of an Italian banker more than 20 years ago.
Calvi is thought to have upset the mafia
Roberto Calvi, chairman of a private bank which collapsed with spectacular losses, was found hanging beneath Blackfriars Bridge across the Thames River.
At first he was thought to have commited suicide, but Italian police believe he was murdered by the Mafia as punishment for pocketing money they had asked him to launder.
Four people were charged earlier this summer and it is thought the aim of the new investigation in London is to help the Italian prosecutor.
Calvi, nicknamed God's Banker because of his Vatican connections, fled Italy after the private bank he chaired, the Banco Ambrosiano, collapsed.
The suicide theory was questioned after forensic tests recently concluded in Germany suggested he had been murdered.
Detective Superintendent Trevor Smith, of the City of London Police, has been asked to begin inquiries into the case on behalf of Dr Luca Tescaroli, the Rome magistrate in charge of the Italian prosecutions.
Calvi key dates
1971: Becomes president of Banco Ambrosiano
1981: Convicted of corruption, but bailed pending appeal
11 Jun 1982: Leaves Italy with a suitcase full of documents
19 Jun 1982: Body found
Jul 1982: Suicide verdict
Jul 1983: Open verdict at second inquest
1997: Italian police charge two with murder
Oct 2002: Forensic report says Calvi murdered
Jul 2003: Four people charged in Italy in connection with Mr Calvi's death
The City of London Police confirmed the "circumstances surrounding Roberto Calvi's death are currently under active investigation".
Calvi's son, Carlo, told BBC News Online the news was "very encouraging" and he said he planned to travel to London from his home in Canada to help assist the police.
The four people facing trial in Italy in connection with Mr Calvi's death are:Pippo Calo, a Mafia gangster already serving a long prison sentence, Flavio Carboni and Ernesto Diotallevi, described as go-betweens and Mr Carboni's Austrian girlfriend, Manuela Kleinszig.
Mr Carboni's lawyer, Renato Borzone, has already accused prosecutors of "relying on a phoney testimony by mafia turncoats" to make their case.
Calvi was found hanging from scaffolding beneath Blackfriars Bridge in central London in June 1982 with bricks in his pockets and $15,000 on him.
He had arrived in London on bail, having been convicted of corruption in Italy.
A coroner initially recorded a verdict of suicide but a second inquest returned an open verdict on the 62-year-old banker.
Carlo Calvi wants a third inquest to look into his father's death in the light of a report by Professor Bernd Brinkmann, who reconstructed the scaffold which was underneath the bridge in June 1982.
Mr Brinkmann concluded Calvi could not have got up the scaffold to hang himself.
Calvi was director-general and president of the Banco Ambrosiano, Italy's largest private bank, when it collapsed.
He was also a central figure in a complex web of international fraud and intrigue.
At the time of his death billions of lire was missing from Banco Ambrosiano's accounts.
Investigators probed the bank's close links with the Vatican's bank, the Institute of Religious Works.
The Vatican denied legal responsibility for the bank's downfall but acknowledged "moral involvement", and paid $241m to creditors.
Italian prosecutors say they believe Calvi was murdered by the Sicilian Mafia and mainland Italian mobsters, the Camorra, as punishment for pocketing money they had asked him to launder.