Ananova:

The head of Bletchley Park spy museum is confident that the stolen Enigma code machine will be returned after she spoke directly to one of the mystery men demanding £25,000 for the encrypter.

Director Christine Large said she was contacted at 4.30am yesterday, just hours after the ransom deadline expired, and believed the machine would be returned when the museum pays the ransom.

She said police have given "certain assurances" to the unidentified men, who claim not to have stolen the machine but to have bought it in good faith and were demanding immunity from prosecution as well as the ransom money.

The Second World War code breaking centre, from where the £100,000 Enigma was stolen in April, has received letters threatening to destroy the machine if the demands were not met.

Ms Large told the BBC: "We had a deal but there was a fear that the machine might be destroyed if the police did not give certain assurances. These assurances have been made now and they have gone some way to being accepted.

"I am sure the machine will be back at Bletchley Park soon, for all to enjoy."

She said the £25,000 ransom was the going price for a standard Enigma machine in good condition, supporting the theory that the people selling it did not steal it themselves.

"Clearly, the machine was stolen but we don't believe it was stolen by the people who are in possession of it now," she said.

"There are a lot of things suggesting that we have got someone here who bought in good faith and would like to get out of the heat and return the machine to us but, obviously, doesn't want to be out of pocket at the same time."

The former spy headquarters in Bletchley, near Milton Keynes, Bucks, has been given the ransom money by a generous donor.

Enigma's capture by the Royal Navy in May, 1941 proved to be a turning point in the war. The encrypter, used by the German navy, to direct U-boat attacks on Allied convoys, was cracked by Bletchley Park's team of experts.