Why did Hitler's deputy Rudolf Hess embark on his disastrous "peace-making" mission to Scotland?
The Nazi kingpin was captured when the plane he was flying crash-landed in a Renfrewshire field.
Theories as to why Hess flew to Scotland, supposedly to engage in peace talks, range from him being lured by the British Secret Service to speculation that he was "deranged".
Now however, a document has been discovered in a Russian archive which suggests Hess was following the orders of his Fhrer.
The discovery is a 28-page notebook found in the files of the Russian Federation in Moscow.
It contradicts the theory that Hess piloted a Messerschmitt to Scotland in a bid to negotiate between the Reich and Winston Churchill without the knowledge of Hitler or other commanders of the regime.
The document was written in 1948 by Major Karlheinz Pintsch, the long-time adjutant to Hitler's deputy Hess, who was captured by the Soviets and spent years undergoing torture and interrogation at their hands.
In it he wrote that Hitler hoped that an "agreement with the Englishmen would be successful".
Pintsch's interrogation transcripts which were also found in the same archive in Moscow as his notebook, show that Hitler "did not seem surprised, nor did he rant and rave about what Hess had done".
• I was Hess's guard in Spandau and I can't believe he flew to Scotland without his Fhrer's approval
"Instead, he replied calmly: 'At this particular moment in the war that could be a most hazardous escapade'."
The transcripts also recorded Pintsch as saying: "Hitler then went on to read a letter that Hess had sent him. He read the following significant passage out aloud. 'And if this project… end in failure… it will always be possible for you to deny all responsibility.
"Simply say I was out of my mind."
That is what both Hitler and Churchill later did.
The latest revelations could mean a dramatic rewriting of what has been the accepted view ever since Hess landed alone all those years ago - that he was an unhinged individual acting without any authority from the regime whatsoever.
If Pintsch's diary is correct then Hitler distancing himself from Hess after the peace mission failed looks to have been just a face-saving ploy.
The party line after Hess was picked up in Scotland was that he was deranged and had made the trip to Britain under his own steam to try to initiate peace negotiations with the Duke of Hamilton.
Hess began his solo flight on 10 May, 1941, from Augsburg in Germany, destined for Dungavel House, the home of the Duke of Hamilton, near Strathaven.However, he was unable to locate the landing strip at the airfield so he bailed out and parachuted into a field at Floors Farm, Eaglesham, where he was taken prisoner by a farmer wielding a pitchfork.
Hess survived the war and was tried at Nuremberg for war crimes. He was sentenced to life imprisonment and spent more time behind bars than any other Third Reich leader before taking his own life in Spandau Prison near Berlin in 1987, aged 93.