"A new archive has revealed the BBC's role in secret activities during World War Two, including sending coded messages to European resistance groups.
Documents and interviews, released by BBC History, include plans to replace Big Ben's chimes with a recorded version in the event of an air attack.
This would ensure the Germans did not know their planes were over Westminster.
BBC programmers would also play music to contact Polish freedom fighters.
Using the codename "Peter Peterkin", a government representative would provide staff with a particular piece that would be broadcast following the Polish news service."
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