LONDON: They were the secret intelligence files that turned second world war history on its head with “revelations” of British collaboration with the Nazis.

British agents used the royal family to deceive the Nazis into expecting a pro-German putsch. The Duke of Windsor leaked secrets to help Hitler. And, most sensationally of all, SS chief Heinrich Himmler was murdered by secret agents on Winston Churchill’s orders.

The elaborate claims, contained in three separate books by the historian Martin Allen and based on previously unseen documents, read like the stuff of spy fiction. As it turned out, they were.

Details of an investigation by the UK National Archives into how forged documents came to be planted in their files have uncovered the full extent of deception. Officials discovered 29 faked documents, planted in 12 separate files at some point between 2000 and 2005, which were used to underpin Allen’s allegations.

Police interviewed Allen, who is believed to be the only person to check out all the files that contained the forged documents. After a 13-month police investigation, the Crown Prosecution Service (UK agency responsible for public prosecution of criminal cases) decided that it was not in the public interest to prosecute, in part because of Allen’s deteriorating health. Allen has repeatedly refused to comment but has previously denied involvement in the forgeries.

Documents from the investigation, including internal correspondence, witness statements to police and forensic science evidence, were posted on the National Archives website over the weekend.

Officials believe this is the most serious case of fraud of its kind anywhere in the world. They have overhauled security at the archives, the official record of 900 years of British government from the Domesday Book on, based in Kew, south-west London. Public reading rooms are now subject to regular patrols and three months ago security cameras were installed to keep an eye on readers. “This is a one-off case, both nationally and internationally,” said a spokesperson. “The papers we’ve released show how seriously we took the situation.”

The investigation found an almost amateurish level of forgery: telegrams and memos contained factual inaccuracies; letterheads had been added using a laser printer; forged signatures were pencilled beneath the ink; and the text of the 29 documents occasionally in conspicuously modern language was typed on just four typewriters. All the documents were used to support Allen’s claims.

In his 2002 book, Hidden Agenda, he suggested the Duke of Windsor helped the Germans to conquer France by slipping secrets to the Nazis via a German spy who acted as intermediary. The claim relied on five bogus documents, including a letter purported to be from the Duke to Adolf Hitler in 1939.

The next year more bogus documents were used to support Allen’s claims, in The Hitler/Hess Deception, about the motives behind the escape of Rudolf Hess, Hitler’s deputy, to Scotland in 1941.

His final book, two years later, Himmler’s Secret War, claimed that Himmler did not, as was widely believed, commit suicide after his capture, but was murdered by intelligence agents on the orders of Churchill. Included in Allen’s evidence was one forged letter purporting to be written by John Wheeler-Bennett, a Foreign Office official, in which he says he has been “giving some serious thought to the little H (Himmler) situation”.

To avoid Himmler giving evidence, or supplying information to American intelligence, Wheeler-Bennett supposedly concluded: “Steps will therefore have to be taken to eliminate him as soon as he falls into our hands.”

In 2005, when the National Archives investigation found 17 documents were fakes, officials called in police.

A witness statement from one archivist, Louise Atheron, finds that even where Allen uses citations from National Archives documents that were genuine, he was guilty of “significant exaggerations” and “very fluid evidence” to stand up dubious claims.

“The National Archives views anything that compromises the integrity of historical information very seriously,” said David Thomas, the archives’ chief information officer.—Dawn/The Guardian News Service