Defend the Realm: The Authorized History of MI5

An unprecedented publishing event: to mark the centenary of its foundation, the British Security Service, MI5, has for the first time opened its archives to an independent historian. The book reveals the precise role of the Security Service in twentieth-century British history, from its foundation by Captain Kell of the British Army in October 1909, through two world wars, up to and including its present roles in counterespionage and counterterrorism. The book describes how MI5 has been managed, what its relationship has been with government, WHERE it has triumphed, and where it has failed. In all of this no restriction has been placed on the judgments made by the author.

Defend the Realm also reveals the identities of previously unknown enemies of the United Kingdom whose activities have been uncovered by the Service, adds significantly to our knowledge of many celebrated events and notorious individuals, and definitively lays to rest a number of persistent myths....

The New York Times - Ben Macintyre

In order to write this compendious but highly readable book, Christopher Andrew…and his team of researchers plowed through some 400,000 MI5 files. Marking the 100th anniversary of the service, Defend the Realm shines a penetrating light into some of the darkest corners of a secret world. It is not only a work of meticulous scholarship but also a series of riveting and true spy stories.