The Italian navy has sealed off access to a huge underwater wreck from the Second World War, whose onboard stash of explosives was being raided by the ’Ndrangheta Mafia to make bombs.

The crime group, which has often left explosive devices outside the offices of magistrates, had access to the 700 tonnes of TNT in the hold of the 150-metre vessel Laura C, which had been heading for Naples from the port of Taranto when it was sunk by a British submarine in 1941.

It wasn’t until the 1990s that the authorities became aware of the dangerous cargo that lies 50 metres below the waters off the coast of Calabria. When evidence emerged that ’Ndrangheta mobsters were plundering the explosives, the police and navy set about sealing off the entrances to the cargo.

Admiral Eduardo Serra, of the Italian navy, said it “had not been easy because we were working in very difficult conditions at a depth of more than 50 metres”.