MI6 drew up a secret hit list of key German figures to be assassinated in preparation for the D-Day landings, according to official papers made public for the first time.
The targets included senior Gestapo officers in France as well as logistics experts considered vital to the movements of the German troops who would confront the Allied invasion force, files released by the National Archives show.
The list was prepared at the request of officers in the headquarters of General Dwight D Eisenhower, the Allied commander in charge of the Operation Overlord landings on the Normandy beaches.
But the plan was dropped less than a month before D-Day amid concerns about its legality and fears that it would lead to reprisals against Allied prisoners of war being held by the Germans.
It began with a memorandum dated April 15, 1944 from Charles Peake, a British political officer in Eisenhower's HQ, with the eye-catching heading "Assassination Priorities for Overlord".
Peake suggested the list could include key German commanders responsible for the defence of France, such as Field Marshals Erwin Rommel and Gerd von Rundstedt, as well members of the Vichy puppet regime.
"The Chief of Staff has asked me to look at this, and to advise him about suitable candidates to who attention might be paid, prior to, on and after 'D-Day," he wrote.
"On the German side, Stulpnagel, Rundstedt and Rommel look likely, but there may be some Vichy collaborators whose removal from the scene would assist."
A handwritten note at the bottom of the memo added that while "it might be of advantage" if a number of Vichy figures were "bumped off at the right moment" it should be left to the Free French to deal with the matter.
Peter Loxley, a senior Foreign Office official, agreed that assassinations carried out by the French resistance might be "relatively plain sailing", but warned targeting German officers was another matter.
"If the proposal is that the Allies, if and when they capture Rommel should have him speedily put to death rather than treat him as a prisoner of war, all sorts of large issues, such as our policy in regard to war criminals, at once arise," he wrote.
"I am having the political issues urgently examined here."
But MI6 chief Stewart Menzies - known throughout Whitehall simply as "C" - made no secret of his distaste for the idea and the plan was effectively quashed two days later by Victor Cavendish-Bentinck, the chairman of the Joint Intelligence Committee.
Among other secrets revealed are:
:: The Duke of Windsor - then Edward VIII - was secretly bugged in 1936 during the final days before his abdication on the order of his own ministers.
The action suggests an extraordinary breakdown of trust between the uncrowned King and his ministers as he wrestled with his decision as to whether he should give up his throne or Wallis Simpson, the woman he loved.
:: MI6 wanted to mount a violent Cold War campaign of subversion and black propaganda to undermine the Soviet Union.
The tactics proposed ranged from minor disruption - throwing stink bombs at Communist Party meetings - to the "liquidation" of selected individuals in Russia and its Eastern Bloc allies. The plan was blocked by Foreign Office officials.
:: A British intelligence officer caused embarrassment to his political masters through his penchant for dressing up as a woman.
Lieutenant Colonel Dudley Clarke, a key figure in British intelligence in the Middle East in the Second World War, set alarm bells ringing in Whitehall when he was arrested in Madrid dressed as a woman.
He told Spanish police he was a novelist and had "wanted to study the reactions of men to women in the streets".