The technical and tactical innovations that developed in the vital naval battle of the Eastern Theatre of World War II. This was an extra on the VHS release of this series.

Discussed are the efforts to break the Enigma Code and the role played by the Colossus computer, designed by T.H. Flowers. In 1977 the Colossus was still on the secret list, so details are fairly sparse, but the programme benefits enormously from an interview with Tommy Flowers. There are also valuable contributions from others present at Bletchley Park during WW2 such as Gordon Welchman, Harry Golombek and Peter Calvocoressi.

The account of how the British scientific effort to discover and counter a dangerously effective new kind of Nazi Germany magnetic naval mine.

An examination of various innovative secret prototype weapon and vehicle designs of World War II, and their military potential.

The development and use of Nazi Germany's V-1 and V-2 missile programs.

The development of radar and its role in World War II air warfare.

The fight by British intelligence to counter Nazi Germany's secret radio navigation systems for their bombers.