Police have begun a murder inquiry into the death of the Italian banker Roberto Calvi who was found hanging from Blackfriars Bridge, central London in 1982.

Mr Calvi, the president of Banco Ambrosiano, had bricks and thousands of pounds in cash in his pockets. His death came shortly after the bank, which had close ties with the Mafia, the Vatican and the Italian freemasonry, collapsed with debts of £800m.

Calvi, known as "God's banker" because of his Vatican links, was initially believed to have killed himself, but the Italian authorities now intend to prosecute four people, including a Mafia boss, for murder. City of London Police said yesterday the case was being "actively investigated" using forensic techniques not available at the time of his death.

A team led by Detective Superintendent Trevor Smith will conduct the inquiry and is likely to revisit Blackfriars Bridge. No officers who investigated the original case are still serving with the force.

A police spokesman said: "The decision was made partly because we've reviewed the whole case and partly because we are working closely with our counterparts in Italy. We've found a number of lines that, even 21 years later, merit looking more closely at the case."

Calvi died after being implicated in Italy's biggest post-war banking scandal. His death was initially recorded by a British coroner as suicide. However, following protests from his family, who have consistently maintained that he was murdered, a second inquest took place recording an open verdict.

Italian prosecutors believe Calvi was murdered in a crime connected with money-laundering. Last year, a panel of forensic scientists commissioned by a Rome tribunal concluded that he was killed.