Operation Bernhard was the name of a secret German plan devised during World War II to destabilise the British economy by flooding the country with forged Bank of England £5, £10, £20, and £50 notes.
The plan was directed by, and named after, SS Major (Sturmbannführer) Bernhard Krüger, who set up a team of 142 counterfeiters from among inmates at Sachsenhausen concentration camp at first, and then from others, especially Auschwitz.
Beginning in 1942, the work of engraving the complex printing plates, developing the appropriate rag-based paper with the correct watermarks, and breaking the code to generate valid serial numbers was extremely difficult, but by the time Sachsenhausen was evacuated in April 1945, the printing press there had produced 8,965,080 banknotes with a total value of £134,610,810. The notes are considered among the most perfect counterfeits ever produced, being extremely difficult although not impossible to distinguish from the real thing.
Although the initial plan was to destabilise the British economy by dropping the notes from aircraft, on the assumption that while some honest people would hand them in most people would keep the notes, in practice this plan was not put into effect.