Four people have been charged with murder over the 1982 London death of Italian banker Roberto Calvi.
Calvi was chairman of Banco Ambrosiano
Calvi, known as God's banker because of his close ties to the Vatican, was found hanging under Blackfriars Bridge.
The suspects are Flavio Carboni, his ex-girlfriend Manuela Kleinzig and Pippo Calo and Ernesto Diotallevi - both said to have Mafia ties.
The four are due to go on trial in October. Calvi's family have always said that he did not kill himself.
An initial inquest verdict of suicide was quashed and the Calvi case has remained unsolved.
Correspondents say a trial is likely to expose the murky Mafia underworld and financial scandals.
Prosecutors are expected to claim Calvi was killed to prevent him revealing explosive secrets about Italy's political and religious establishment.
Roberto Calvi was found hanging under London's Blackfriars Bridge with bricks in his pockets and $15,000 on him.
He had come to the UK on bail after having been convicted of corruption in Italy.
The City of London police reopened the murder investigation last September, alongside Italian authorities.