The British Secret Intelligence Service—popularly known as MI6—is the oldest established continuously surviving foreign intelligence-gathering organisation in the world. It has also historically been the most secret department of the British government. Founded in 1909, its existence was not officially acknowledged until 1994. Before then official British representatives had to pretend, sometimes with embarrassing results, that there was no such organisation as ‘MI6’, and even if there was, they ‘couldn’t possibly comment’ about it. Although the agency has had a website since 2005, few details are released about the number of people who work for it or the size of its budget, nor are any of its officers publicly avowed, with the sole exception of the Chief, whose name has been published since 1992. Unlike Britain’s other security and intelligence organisations, MI5 (which covers domestic security, rather like the FBI) and the signals intelligence agency, the blandly-titled Government Communications Headquarters (GCHQ; analogous to the NSA), SIS releases absolutely none of its departmental records to the British National Archives. For almost all of its hundred-year existence, the strict line has been taken that the super-secret work of SIS, gathering foreign intelligence from foreign sources, has been of such vital national importance that no iota of information about it could formally be released to the public. Until now.

The writing of an officially-authorised history of SIS presents challenges for the agency and historian alike. For the outcome not to appear to be some sort of ‘hack house history’ (and thus vitiate its value as a reliable, scholarly and authoritative work) the author has to be given sufficient freedom—or licence—to exercise his or her own critical judgments. The author, too, has to surmount the wisely sceptical assumptions of colleagues who may believe that the fact that he has been deemed suitable for the task may precisely render him unsuitable to produce a rigorous and independent history. Writing to such a commission necessarily involves accepting some constraints on what may be published, but so long as any redactions are limited to genuine matters of national security (though that itself is a matter of potentially differing judgment), and not simply to protect the agency from embarrassment, or to suppress failure or wrong-doing, it ought to be a price worth paying. It may in some degree be invidious that only a single individual is granted uniquely privileged access to what is certainly the ‘Holy Grail’ of British archives, but since it is the case that for the foreseeable future no similar access will be granted to anyone else, then perhaps the risk is worth taking.