By Paul Reynolds
World affairs correspondent, BBC News website
German sabotage agents developed an exploding bar of chocolate and what was probably the first shoe-bomb during WWII.
German agents planned to use exploding bars of chocolate
Photographs of these and other devices, held in the files of the security service MI5, have been cleared for release by the National Archives.
The devices were intercepted by British intelligence in various locations, including Turkey, but there is no evidence that any such bombs were used - and certainly not in the UK.
These ingenious objects got no further than four explosive cans of peas, which were found on German agents who landed in Ireland by small boat and claimed that they hoped to get them into Buckingham Palace. Details of this plot were reported two years ago.
The latest pictures show how a bomb could be hidden inside a chocolate bar and how explosives could be disguised as the soles of a shoe.
It appears therefore that Richard Reid, who tried to blow up an airliner over the Atlantic in December 2001, was not the first would-be shoe bomber.
There were other examples of devices with explosives inside them - a tin of Smedley's plums, lumps of coal, cans of motor oil, shaving brushes and a mess tin.
Also released by the Archives from MI5 files are examples of German wartime propaganda aimed at the British population.
According to the official historian of MI5, Cambridge Professor Christopher Andrew, the German sabotage failure and the low standard of their propaganda are examples of their overall intelligence failure in the war.
"Why was German intelligence and propaganda so much worse than the Russian?" he asked.
"Possibly because Germans did not want to be spies. All German spies in Britain were caught and all were non-German.
"German propaganda was incredibly bad. Some of it was Monty Python stuff. It illustrates the incompetence of German propaganda at the time.
The original shoe-bomb?: explosives disguised as soles
"German espionage and sabotage in Britain reached the level of 100% incompetence in World War II."
One propaganda sheet is so bad that Professor Andrew thinks it might have been a spoof written by British civil servants.
Headed "Naziministerium des 3ten Deutsches Reiches", it says, in English: "To the men of Britain and Eire. You have proved yourselves a race of abject COWARDS unwilling to leave your Mamas' & Wifey's apron strings and FIGHT ME.YOU LICE, VERMIN, SPAWN of PROSTITUTES."
Other bombs would be planted inside coal, plums and motor oil
It goes on and on and includes some anti-Semitic remarks as might be expected.
Other pamphlets were a bit more sophisticated. One, issued before the war, starts: "My dear English reader, you may be surprised to receive a letter from Germany. I am a friend of English-German understanding."
There is also an interesting fake copy of the London Evening Standard, dated February 1940. Its headline reads: "The massacre of the RAF".
However it is so bad as to be laughable and again might even be a spoof.
It has a box in the top left hand corner which reads: "Take French laxative: it will keep you on the run."