The files, whose contents are revealed for the first time in today's Independent, were supplied by the secret service throughout the ill-fated Egypt invasion under Anthony Eden in November 1956. They have been cleared unexpectedly for Public Record Office release.
The information is a careful breakdown of the war's progress, including casualties, enemy deployments and detail that would not have been known at the time, even to Cabinet ministers outside the "war cabinet".
Some files reveal what was not generally known, that British intelligence feared Soviet interference against the British and French. One bulletin talks of "continued indications" that Russian aircraft may be moving into the Middle East.
The release is the latest fruit of an initiative by William Waldegrave, when Minister for Open Government, which has opened up 14,000 files, mainly held by the Ministry of Defence. It was found either there was no longer any reason to hold them back, or that they could be released with only minor deletions.
Files on the Royal Family, previously closed for 100 years, are now considered for opening after 30, along with other official papers, provided there is no national security objection.