'The master' makes third offer to return the Enigma

A third letter offering the return of the stolen Enigma decoding machine for £25,000 has been sent on behalf of a man calling himself "the master". But the author of the letter, who claims to be acting as a gobetween, insists the device is not being held to ransom.

A third letter offering the return of the stolen Enigma decoding machine for £25,000 has been sent on behalf of a man calling himself "the master". But the author of the letter, who claims to be acting as a gobetween, insists the device is not being held to ransom.

The Second World War German encoding machine, worth an estimated £100,000, was stolen in April from the museum at Bletchley Park near Milton Keynes - the wartime Station X where decoding was done. Three letters written in a muddled and archaic language have been sent to the museum explaining that the machine was bought in good faith and that the new owner would return it if he was reimbursed and not charged.

Although the author claims to be writing on behalf of his "master" he is believed to be holding the machine. Each of the letters, which were posted from the West Midlands, was signed using a password. The first two letters were written on typewriters and were authenticated by a photocopy of the machine's serial number, G312.

The latest letter was written on a computer and asked the police for further reassurances that the author will be immune from prosecution. The letter says: "[Press reports] indicated the machine has been held to ransom. This was not and never has been the intention of the new owner. It's never been about claiming money to which the owner does not feel entitled. It's about his honour being restored."

A Thames Valley Police spokesman said: "If he purchased it in good faith and if he can prove that, he could be entitled to the return of his money. We want him to get in touch with us directly to save all this to-ing and fro-ing in the media. Hopefully we are going to get the Enigma back."

The letters have been examined by a decoding expert to establish whether the strange use of language contained a hidden code but nothing unusual was found. Police now believe the most likely explanation is that the strange wording is being used to mask the identity of the author. Detective Chief Inspector Simon Chesterman, who has been leading the investigation, added: "The author is seeking certain reassurances which I feel I will be able to give if he contacts me directly."

The machine was stolen on 1 April at an open day at the museum, when hundreds of visitors passed through. The loss was discovered only at the end of the day.