Because even the most elementary aspects of the British intelligence services - and MI6 in particular - were enveloped in deep secrecy for so long, they remain at once more baffling and more electrifying than they are in, say, America. Whether or not you think it's healthy that George Tenet, the director of the CIA, had to undergo a congressional hearing before he could be confirmed in his job, it certainly robs his role of a little of its mystery. Until MI6 was finally "avowed" under John Major, most people in this country depended, whether directly or not, on the novels of John Le Carre for what they knew not only about the service but also about its relationship with the government of the day.
All this makes the future of "C", the head of MI6, and the question of who is to replace him a more novel subject of public comment than almost any other job in public service. As it happens, there are tentative grounds for believing that the departure of Sir Richard Dearlove isn't quite the premature walkout it appears to be, although it is natural, after all the fuss over the two dossiers used to justify the war in Iraq, to suppose it is.
It rather looks as if an Oxbridge college has already been identified as his next berth. Five years is a normal stint in this extremely demanding job. It's possible that he is simply ready, for prosaic reasons, to move on. And that the government claims that there is nothing deeper to his departure are true.
Which doesn't mean that it isn't interesting. For the question of the succession is bound to ventilate the increasingly complicated relationship between the intelligence services and their political masters.
In the long run, it may do so even more than the inquiry into the death of David Kelly. Lord Hutton's task won't be made any easier if the lamentably crass and tasteless depiction of Dr Kelly as the "Walter Mitty figure" he clearly wasn't, has given away the true government strategy in dealing with the inquiry. That task is already formidable enough. But it looks as if Lord Hutton's remit will make it very difficult for him to look at the larger questions surrounding the process of deciding on a war which, it's worth repeating, was the first anyone can remember to have been fought on the legal and political basis of intelligence alone.
Suppose the Government emerges from the Hutton inquiry with the judge having entirely vindicated the majority decision of the Commons Foreign Affairs Select Committee that neither Alastair Campbell nor anyone else in Government did anything to compromise the integrity of the intelligence it published in the September dossier. That doesn't mean that the question of whether that intelligence justified the decision to go to war has been laid to rest.
This is a more complicated question than it looks. The confirmation of Sir Richard's departure presages a potentially uncomfortable period for John Scarlett, the chairman of the Joint Intelligence committee (JIC), the man responsible for signing off the September dossier, and a possible candidate to replace Sir Richard.
Mr Scarlett, by all accounts an outstanding high flier who was a brilliant head of the Moscow station, is unusual in that for the first time in the Joint Intelligence committee's history, he was appointed to be its chairman after a career inside MI6. Normally the job - the fulcrum of the intelligence services' contact with the government of the day - is given to a conventional, if also high flying, civil servant or diplomat.
The case against Mr Scarlett …