For the scientists working in what Churchill called the small back rooms', the secret war was a continuous battle of move and counter-move - always against time and in the knowledge that mistakes or delay could cost many lives. 2: To See for 100 Miles
Just before the outbreak of the Second World War tall masts spring up around our coasts; a German Zeppelin loaded with radios flies to investigate. The crew hear nothing and the Battle of Britain is half won, for the masts are part of the earliest form of radar and a vital element of our defence system. Then in 1940 a decoded German message gives British scientific intelligence a new code name ' Freya' and the hunt for German radar is under way. Narrator WILLIAM WOOLLARD
Film editors COLIN JONES , CHRIS SPENCER Written and produced by BRIAN JOHNSON