MI5 uncovered a secret Polish plot to assassinate Rudolf Hess after his landing by parachute in Scotland during the Second World War, according to newly disclosed evidence.
The arrival of Hitler’s deputy near the Duke of Hamilton’s Lanarkshire estate in 1941 raised the question of whether British intelligence or members of the aristocracy were trying to broker a secret peace deal with the Nazis.
Although such conspiracy theories subsequently proved unfounded, some British-based Polish soldiers feared Hess’s arrival showed their country was being sold down the river.
After Germany’s invasion of Poland in 1939, many soldiers escaped to Britain and were stationed at bases such as one at Fort William, where there was a Polish military training school.
A group of Polish conspirators from Fort William were determined to prevent a deal between Britain and Germany over their homeland, according to the personal diaries of Guy Liddell, the director of MI5 counter-espionage during the war.
In the summer of 1941, 17 Polish officers and two British accomplices planned to travel south to Aldershot, where Hess was being held at a secret base. They made it only as far as the railway station before they were intercepted by MI5.
The intelligence historian Nigel West, who edited Liddell’s diaries, said that had the assassination attempt been successful, it would have led to the Polish community being severely isolated in Britain.
He said: "At the time, the Polish community were deeply concerned that the British were brokering a deal with the Germans which would allow the Nazis to occupy their country. They felt they were being left out of the war effort and did not have a proper role to play.
"The would-be Polish assassins were abetted by a British soldier called Alfgar Hesketh-Pritchard, who was something of an adventurer and was sympathetic to the Polish plight.
"He also discovered Hess’s location as he had contacts among his guards. After Hess’s flight, the Germans regarded him as a lunatic, but he was useful to Britain to provide information on Hitler, and his capture was a propaganda coup."
Due to the highly restricted nature of their content, Liddell’s journals were codenamed Wallflower and were for many years locked in the director-general’s safe at MI5.
The story behind Rudolf Hess’s flight to Britain is one of the most controversial of the Second World War. The event gave rise to conspiracy theories surrounding the alleged existence of covert peace plans by MI5.
Hess crashed his Messerschmitt at Dungavel, near Glasgow, on 10 May, 1941. On landing, he declared that he had come to meet the 14th Duke of Hamilton.
The duke knew Hess’s friend, Albrecht Haushofer, a member of the German Foreign Office who was determined to find a peace settlement with Britain.
But last year the 14th Duke of Hamilton’s son, Lord James Douglas-Hamilton, the Lothians MSP, publicised other newly declassified documents which proved his father had no idea Hess planned to embark on his peace mission to Britain.
The possibility of a treaty being agreed with the British government is also denied by Liddell, who records on 9 June: "I think the Poles imagine that Hess may be making peace overtures and that this will be listened to by the British government. Nothing, of course, could be further from the truth."
Liddell’s journal also reveals that British intelligence took 12 years to catch the communist spy John Cairncross, following a tip-off from a Russian defector.
Cairncross - the infamous fifth man in the Cambridge spy ring that included Burgess, McLean, Blunt and Philby - was not unmasked until 1951 after more than a decade of passing British secrets to the Russians, according to Liddell.
The Guy Liddell Diaries (Vol 1 1939-1942), edited by Nigel West, published by Taylor & Francis