Many thanks to SWLing Post reader, Jonathan Marks, who shares this video about Luftwaffe Navigation Beams via YouTube–fascinating WWII history:
This episode documented how British Intelligence became aware of various German Luftwaffe Navigation Beams, such as Knickebein, X Gerat and Y Gerat, and the counter measures developed to combat them, in what became known as the Battle of the Beams.
It is largely based on the book Most Secret War written by R.V.Jones who features heavily in the series. This programme contains rare footage of The Blitz including the bombing of Coventry. Interviewees include Albert Speer and AVM Edward Addison.