The history of naval warfare is littered with incidents in which ships were sunk, with great loss of life, due to the enemy having intercepted badly coded or otherwise insecure signals.

Whilst many people are aware of the strategic advantage gained by the Allies during World War Two by the cracking of the ‘Enigma’ code used by the German U-Boat fleet, few are aware that Allied naval codes were similarly cracked by the Germans, leading to significant losses of ships and personnel.

In this expansive study of the subject, Leslie Howson, a former naval telegrapher during World War II, examines the sorry history of careless and unguarded messages sent between Royal Navy and allied ships during two world wars, and the tragic consequences for thousands of seamen who lost their lives due to intelligence all too easily gathered by the enemy.

These lapses of security could have been avoided, he argues, but for the stubborn refusal of the Admiralty to address the problem, and he supplies plenty of detailed evidence to support his claims in a highly informative narrative that encompasses the social, economic and political contexts of its subject matter.

Those with an interest in maritime history, codes and codebreaking and the history of the Royal Navy will find much of interest in this thought-provoking and forthright book, which pulls no punches in its criticism of RN High Command.