As we become ever-more aware of how our governments “eavesdrop” on our conversations, here is a gripping exploration of this unknown realm of the British secret service: Government Communication Headquarters (GCHQ).

A gripping exploration of the last great unknown realm of the British secret service: Government Communication Headquarters (GCHQ).

GCHQ is the successor to Bletchley Park and is the largest and most secretive intelligence organisation in the country. Since the end of the Cold War, it has played a pivotal role in shaping Britain's secret state. Still, we know almost nothing about it.

In this ground-breaking new book, Richard Aldrich traces GCHQ's evolution from a wartime code-breaking operation based in the Bedfordshire countryside to one of the world’s leading espionage organisations.

Packed to the brim with dramatic spy stories – including secret submarine missions, hidden tunnels dug to tap phones and Soviet moles – GCHQ also explores the organisation’s role in tackling some of the most troubling issues of our time: Al Qaeda, privacy and surveillance. Revelatory and brilliantly written, this is the crucial missing link in Britain’s intelligence history.

‘Richard J. Aldrich is an outstanding analyst and historian of intelligence … an important book’ Sunday Times

As we become ever-more aware of how our governments “eavesdrop” on our conversations, here is a gripping exploration of this unknown realm of the British secret service: Government Communication Headquarters (GCHQ).

GCHQ is the successor to the famous Bletchley Park wartime code-breaking organisation and is the largest and most secretive intelligence organisation in the country. During the war, it commanded more staff than MI5 and MI6 combined and has produced a number of intelligence triumphs, as well as some notable failures. Since the end of the Cold War, it has played a pivotal role in shaping Britain's secret state. Still, we know almost nothing about it.

In this ground-breaking new book, Richard Aldrich traces GCHQ's evolvement from a wartime code-breaking operation based in the Bedfordshire countryside, staffed by eccentric crossword puzzlers, to one of the world leading espionage organisations. It is packed full of dramatic spy stories that shed fresh light on Britain's role in the Cold War – from the secret tunnels dug beneath Vienna and Berlin to tap Soviet phone lines, and daring submarine missions to gather intelligence from the Soviet fleet, to the notorious case of Geoffrey Pine, one of the most damaging moles ever recruited by the Soviets inside British intelligence. The book reveals for the first time how GCHQ operators based in Cheltenham affected the outcome of military confrontations in far-flung locations such as Indonesia and Malaya, and exposes the shocking case of three GCHQ workers who were killed in an infamous shootout with terrorists while working undercover in Turkey.

Today's GCHQ struggles with some of the most difficult issues of our time. A leading force of the state's security efforts against militant terrorist organisations like Al-Qaeda, they are also involved in fundamental issues that will mould the future of British society. Compelling and revelatory, Aldrich's book is the crucial missing link in Britain’s intelligence history.