Today in History - May 4: This chocolate bar would kill you in seven seconds
"We have received information that the enemy are using pound slabs of chocolate which are made of steel with a very thin covering of real chocolate," he wrote.
"Inside there is high explosive and some form of delay mechanism."
Fish was asked to draw a diagram of the explosive chocolate as a warning for Churchill.
In the letter, Rothschild revealed one of his agents had seen one of the bomb chocolates.
The explosive would go off seven seconds after the bar was broken.
The first use of the phrase that would lead to the creation of Star Wars Day was printed in anticipation of May 4, 1979.
While May 4 would not be named Star Wars Day until 2011, it would first be used in connection with UK politics.
The Conservative Party placed an advertisement in the Evening Standard which read - "Dear Maggie, May the Fourth be with you."
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