Every day reports were rushed to Churchill, then taken back for security after he had seen them. It is these key reports for the years 1943-45 which have been published.
It can be seen how the head of GCCS, Major-General Sir Stuart Menzies, makes summaries of the contents for the Prime Minister, signed with his codename C, in characteristic green ink, and Churchill, in scrawling red ink, signs his initials.
The papers give an illustration of how comforted Churchill must have been to know what the enemy was thinking, and the sense of superiority this must have given him. A failed plot among senior German army officers to assassinate Hitler in July 1944, and reaction to it in Japan and Germany, is duly passed to the PM within days.
On 25 July, the Japanese ambassador in Berlin writes to the foreign ministry in Tokyo: 'The attempted assassination of Hitler on 20 July is the greatest misfortune for Germany since the outbreak of the war.' Churchill has ringed in red the words 'greatest misfortune'.
On 23 July, Churchill learns: 'To mark the preservation of his life from the murderous attack the Fuhrer has granted the wish of the Wehrmacht (army) that the German greeting (Nazi salute) be introduced in place of the military salute, as the outward sign of the unshakeable national socialist ideology of the Wehrmacht.'
On 7 June 1944, Churchill received a report from the Siamese ambassador in Berlin to his government in Bangkok that petrol rations for all diplomats had been cut by one-fifth - and his pessimistic conclusions for the German war effort.
Very few of Churchill's reactions are recorded. But on one occasion, on 14 April 1944, he is sent a circular from the Foreign Ministry in Berlin to all embassies, which suggests Eden, the Foreign Secretary, and Churchill himself are both likely to be forced to resign in an internal political crisis. Churchill has written under this in red ink: 'Amusing. Eden ought to see this]'Reuse content