As described in the UK National Archives:
In the unprecedented international situation existing following the end of the second world war, the Cabinet instituted the preparation of the War Book. ... (It) was assembled in three parts reflecting pre-Precautionary Stage matters, the Precautionary Stage, and War. The War Book specifies the actions to be taken by ministers and officials in each of these periods. ... The war books have been subject to a virtually continuous process of revision and amendment.
The photo is from the website www.burlingtonbunker.co.uk; the caption reads, "The BBC's underground broadcasting studios, which the prime minister would have used to address the nation."
* Links to declassified files (from website www.coldwaronline.co.uk): @
* Various documents (from @wellbright): @* "The Secret State: Old and New" (lecture by Peter Hennessy; from Journal of Royal Air Force Historical Society): @
* "The Thin Wisps of Tomorrow" (lecture by Hennessy; from Journal of the International Liberal Group): @
* "Catch-up History and the Cold War" (lecture by Hennessy; delivered to Friends of the National Archives": @
* "Peering into Britain's Cold War Past" (BBC video): @
* "Rehearsing the end of the world" (BBC audio): @
* "1961 files: codeword to enter secret bunker at the end of the world" (from The Telegraph newspaper): @
* "Wiltshire's Underground City" (from BBC): @