it actually happened
MI5 files released now -
http://www.bbc.co.uk/news/uk-17070943
Nazi counterfeiting "destroyed" confidence in the British currency in Europe by the end of World War II, according to newly released MI5 files.
A 1945 report in the National Archives suggests Germany began production of the fake notes five years earlier in a bid to undermine sterling.
Notes began to enter neutral countries by D-Day and the Bank of England issued the first of two recalls. etc