《捍衛王國》的齣版在齣版業界是史無前例的：為紀念英國軍情五處成立一百周年，該機構首次授權獨立曆史學傢接觸其機密檔案。本書揭示瞭軍情五處在20世紀英國史中發揮的確切作用，從1909年10月英國陸軍上尉凱爾建立該機構，隨後經過兩次世界大戰，到如今還發揮著反間諜反恐的作用。本書講述軍情五處是怎樣運作的，它與政府間維係著怎樣的，在哪些方麵成功瞭又在哪些方麵失敗瞭。作者對這一切發錶瞭暢快淋灕的評判。

本書也披露瞭先前不為人知的英國的敵人的身份，他們的行蹤被該機構揭穿瞭，極大增加瞭我們對很多著名事件以及臭名昭著的人物的瞭解，無疑破解瞭很多長期的謎團。最重要地是，揭露瞭英國先前最隱秘組織的所在地。鮮有書籍能讓我們對上個世紀的英國史即刻瞭解那麼多。

To mark the centenary of its foundation, the British Security Service, MI5, has opened its archives to an independent historian, the first time any of the world's leading intelligence or security services has taken such a step. "The Defence of the Realm", the book which results, is an unprecedented publication. It reveals the precise role of the Service in twentieth-century British history, from its foundation by Captain Kell of the British Army in October 1909 to root out 'the spies of the Kaiser' up to its present role in countering Islamic terrorism. It describes the distinctive ethos of MI5, how the organization has been managed, its relationship with the government, where it has triumphed and where it has failed. In all of this, no restriction has been placed on the judgements made by the author. The book also casts new light on many events and periods in British history, showing for example that through well-placed sources MI5 was probably the pre-war department with the best understanding of Hitler's objectives, and had a remarkable willingness to speak truth to power; how it was so astonishingly successful in turning German agents during the Second World War; and that it had much greater roles than has hitherto been realized during the end of the Empire and in responding to the recurrent fears of successive governments (both Conservative and Labour) and or Cold War Communist subversion. It has new information about the Profumo affair and its aftermath, about the 'Magnificent Five' and about a range of formerly unconfirmed Soviet contacts. It reveals that though MI5 had a file on Harold Wilson it did not plot against him, and it describes what really happened during the failed IRA attack in Gibraltar in March 1988. When Rab Butler was appointed Home Secretary with responsibility for the Security Service in 1957 he didn't even know where its headquarters were. "The Defence of the Realm" now describes this previously extremely secretive organization more fully than any previous book - and identifies all its main buildings on the end papers.

Christopher Andrew is Britain's leading historain of intelligence, Professor of Modern and Contemporaty History and former Chair of the Faculty of History at Cambridge University. He is also chair of the British Intelligence Study Group, Founding Co-Editor of Intelligence and National Security, formaer Visiting Professor at Harvard, Toronto and the Australian National University, and a regular presenter of BBC Radio and TV documentaries, His fifteen previous books include The Mitrokhin Archive and The Mitrokin Archive II, and a number of path-breaking studies on the use and abuse of secret intelligence in modern history.