Blackmailers are increasingly demanding cryptocurrencies that offer anonymity to usersAlamy

Kidnappers are becoming harder to track down as they demand cryptocurrencies as ransom payments, police have said.

Scotland Yard said that kidnap investigations were growing increasingly complex because of the emerging use of cryptocurrencies instead of hard cash.

The National Crime Agency has been working with forces to develop strategies to capture kidnappers and blackmailers demanding cryptocurrencies. It is easier to track criminals who rely on cash because the serial numbers of banknotes can be traced and the location of any handover offers clues to the kidnappers’ whereabouts.

Cryptocurrencies can offer anonymity to users. They are digital cash, with no coins or notes to carry around, and are transferred via a computer. Transactions are recorded and though they may be made public are linked only…