A British intelligence agency may have had a part in Adolf Hitler’s attempt to take his life, as an author claims.

Operation Valkyrie failed plot was orchestrated by Colonel Claus von Stauffenberg. It saw a suitcase bomb planted and detonated at Hitler’s Wolf’s Lair Headquarters.

While four people were killed by the explosion, Hitler, who was left with an injured eardrum and perforated ears, survived the attack. He was then executed alongside many other conspirators.

Up until now, the assassination attempt, which was immortalised in 2008 Hollywood thriller Valkyrie, was believed to have been the sole work of Germans – although it was known that British-made explosives and triggers were used.

A previously classified file that was kept secret from the National Archives, but was finally declassified in 2007, revealed that Otto John was a German-based lawyer who was involved in planning the attack.

According to this file, John was assigned the codename “Whisky” and met his Mi6 bosses 12 times before the attempted killing of Hitler. This is what’s now known as The 20 July Plot.

His role is said to be that of an intermediary between Colonel George Hansen and Britain’s spy chiefs.

Nigel West discovered the file when he was doing research on Hitler’s Nest of Vipers. It is a history of the German intelligence agency.

MailOnline was told by John that John was a well-known historical figure. However, it was not known that Whisky was his codename. He was meeting Rita Winsor and Graham Maingot for the first time in two years prior to 20 July.

Jokingly, the historian said that while the two might have been just having “cosy meetings” and drinking tea together, the likelihood is that they were discussing the plot of 20 July. “The historical implications of these events are huge,” Mr West stated.

Britain's intelligence service may have played a role in the 1944 attempt on the life of Nazi dictator Adolf Hitler, an author has discovered. Above: The aftermath of the 20 July plot

A British intelligence agency may have played an important role in Adolf Hitler’s attempt to kill him, according to author. Above: Aftermath of the plot on 20 July

A group of disillusioned soldiers, led by nobleman Count von Stauffenberg and army officers who were aware that Germany was going to lose the war, devised the 20 July plan.

Following months of planning with his conspirators, von Stauffenberg planted the bomb inside a conference room in Hitler’s East Prussian Headquarters, where Hitler was currently meeting his advisers.

Tom Cruise played Von Stauffenberg as the main character in the film.

The plan was thwarted when someone accidentally moved the bomb-laden briefcase next to a leg. This meant that it took much of the blast.

Up until now, the assassination attempt was believed to have been the sole work of Germans – although it was known that British-made explosives and triggers were used. But a previously top-secret file (pictured) which had until recently lain unread in the National Archives since it was declassified in 2007 has revealed that conspirator Otto John, a German lawyer, was working for Mi6 when the attack took place

Up until now, the assassination attempt was believed to have been the sole work of Germans – although it was known that British-made explosives and triggers were used. However, the National Archives has recently declassified a top-secret file that was previously unread. It revealed that Otto John, a German attorney, was the conspirator.

Written by official Herbert Hart, the most revealing passage details how John had been 'an S.I.S [MI6] agent for two years and whom the Germans are now hotly pursuing on the footing that he was party to the attempt on Hitler's life on July 20'

The most interesting passage, written by Herbert Hart official, details John’s time as an S.I.S. [MI6]Two years as agent, and the Germans have been pursuing him on the basis that he participated in Hitler’s attempt to kill his life on July 20′.

The file reveals how John (pictured) was given the codename of 'Whisky' and met with his Mi6 handlers a total of 12 times in the lead-up to the attempt to kill Hitler, which is now popularly known as the 20 July plot

The files reveal how John (pictured) was assigned the codename “Whisky” and met 12 times with his Mi6-handlers in the run up to Hitler’s attempt to kill him. This is what’s now known as the plot of 20 July.

However, 4 people were killed, 3 of them German officers. Hitler also had a perforated eardrum and his trousers were stained and damaged.

Stauffenberg, along with several other people, were killed in Berlin’s courtyard at the Bendlerblock.

Some others were hanged from piano wires in Berlin’s Gestapo Prison of Ploetzensee.

After the plot was foiled, John attempted to escape Germany using the MI5 document.

The unsuccessful Operation Valkyrie plot, which took place on July 20 in the penultimate year of World War Two and was masterminded by senior German officer Colonel Claus von Stauffenberg (pictured above), led to a planted suitcase bomb being detonated inside Hitler's Wolf's Lair headquarters

Actor Tom Cruise played the officer in 2008 film Valkyrie

Operation Valkyrie, an unsuccessful plot that was orchestrated by Colonel Claus von Stauffenberg in Germany’s penultimate World War Two year, saw a bomb-laden suitcase explode inside Hitler’s Wolf’s Lair. Right: Tom Cruise played the role of Valkyrie’s officer in 2008.

The most striking passage, written by Herbert Hart official, details John’s time as an S.I.S. [MI6]Two years as agent, and the Germans have been pursuing him on the basis that he was involved in Hitler’s attempt to kill his life on July 20th’.

John managed to flee Germany as he worked for Lufthansa, so he wasn’t suspected of being on a flight from Germany to Madrid.

Hitler’s soldiers discovered that he was involved and arrested him before executing his brother.

John made it to Madrid and was then flown to England, where he later became the head of West Germany’s intelligence services.

The new file, Mr West stated, is “absolutely amazing”. A MI6 parallel document is also referenced in the file, which was never discovered.

After months of preparation with his co-conspirators, von Stauffenberg placed the bomb in a conference room at Hitler's East Prussian headquarters, where the dictator was meeting with his aides and military advisers. Above: von Stauffenberg is seen far left standing next to Hitler as he meets an official five days before the attack

Following months of planning with his conspirators, von Stauffenberg dropped the bomb into a conference room in Hitler’s East Prussian Headquarters. This was where Hitler and his military advisors were meeting. Above: Von Stauffenberg can be seen standing far left next to Hitler five days prior to the attack.

Along with his perforated eardrum, Hitler's trousers (pictured above) were also left singed and tattered

Hitler’s pants (pictured above), along with his perforated ears, were also singed and torn.

It could be more detailed about John’s relationship to the intelligence service if it is still available.

West stated: “Based on the astonishing evidence it is inconceivable that British didn’t know, have an opinion about, or participate in this momentous plot.”

“We now know that Otto John is an MI6 asset. He also has a large MI6 dossier. This will reveal the British role in Valkyrie, and Otto John’s role as the “missing link”.

The historian found the MI5 file amid an ongoing legal battle led by German aristocrat Prince Frederick Solms-Baruth

His grandfather was involved in the 20 July plot

He found the MI5 files amid ongoing legal proceedings led by German aristocrat Frederick Solms Baruth. His grandfather was in part of the 20 July plot.

The family's 17,000 acre estate, Baruth castle, was a key headquarters for the plotters, where they met and discussed their plans whilst horse riding. Prince Frederick's grandfather, Prince Friedrich zu Solms-Baruth III, was arrested and tortured by the Nazis after his role was discovered. He was forced to transfer ownership of his family's estates to Hitler's deputy Heinrich Himmler. After the war ended, the family never got their land back and it is now owned by the German state

Baruth Castle, a 17,000-acre family estate was the key hub for plotters. It allowed them to meet and discuss their plans while riding horses. The Nazis tortured Prince Frederick’s grandfather Prince Friedrich zu Solmszu-Baruth III after he was found out about his involvement. After being exposed, Prince Friedrich zu Solms-Baruth III was taken into custody and tortured by the Nazis. He had to give Heinrich Himmler his estates. Their land was not returned to the family after the war, and is now the property of the German government

The MI5 files were discovered by the historian during a lengthy legal battle between Prince Frederick Solms Baruth and the German aristocrat. Solms Baruth’s grandfather was involved with the 20 July plot.

Baruth Castle on 17,000 acres was the family’s key headquarters. Here they discussed and shared their plans while horse-riding.

After his role in the discovery of Prince Frederick’s role, Prince Friedrich zu Solmsbaruth III was captured and tortured.

His family estates were transferred to Heinrich Himmler, Hitler’s deputy. 

After the war, their family did not get their land back. It is now in the hands of the German state.

Prince Frederick will appear at court in an effort to get the land back.