“MISS X” OF MI6 TOOK THE STAND, invisibly, in the Diana, Princess of Wales inquest this week and offered a small peek into the arcane world of spookspeak, the strange, fertile and semi-secret language of spying. Miss X revealed that to assist the earlier investigation into the crash, she had temporarily been granted “God's access” to the files of the Secret Intelligence Service (SIS): the term apparently refers to the topmost degree of security clearance, a level usually reserved for the three most senior officials of the service.

The term “God's access” has never before been deployed in public. Before this week, it did not even exist on the internet. But it is most certainly part of the lexicon now: “Carruthers, if we are going to get to the bottom of this parliamentary expenses fiddling, we are going to need God's access to all MPs' expenses claims.” Like all small, self-contained tribes, the intelligence community has always communicated in its own patois, a language For Your Ears Only. Euphemisms thrive in this world of disguises, half-truths and deception: sleepers and cleanskins, moles and bagmen, dead drops, honeytraps and wet jobs. Some of the language seems to have evolved organically and internally because so little of what happens in espionage can be described openly: just as agents and operations are designated by codewords, so the language of spying is itself an elaborate code, in which nothing may be described as what it is. A bodyguard is a “babysitter”, a false passport is a “shoe”, forged by a “cobbler” and so on.

Such words serve a dual purpose: to clarify matters for those who speak the language - the “Friends” - and to confuse or mislead those who do not.

The East German Stasi deployed an estimated 400,000 agents and informants, and developed a secret language so complex and verbose that anyone trying to sift through the files of the secret police requires the Dictionary for State Security: 500 pages long, with 51 separate subheadings and containing almost 1,000 special jargon terms.

Many of the terms we associate with spying have been borrowed or adapted from literature. John le Carré is the master of spy language, having forged a lexicon so rich and memorable that genuine spies have adopted it: lamplighters (watchers, safe-house men), pavement artists (shadowers), and above all, moles, the spies lurking within the “Circus”.

Aldrich Ames, the American CIA agent convicted in 1994 of spying for the Soviets and Russians, has frankly acknowledged the linguistic debt owed to le Carré. “‘Mole' is the best example of jargon created by literary or journalistic use,” Ames told The New York Times (in a letter from prison). “Whether or not SIS ever used it, it gradually entered use in the American community from John le Carré's novels.” There is a natural link between the language of fiction and that of spying. As Graham Greene (who joined MI6 in 1941) demonstrates so memorably in Our Man in Havana, the spy is already part novelist, turning his imagination into truth. As a naval intelligence officer, Ian Fleming referred to his various schemes to baffle and confuse the enemy as “plots”; transferring those plots to fiction after the war, to create the most memorable fictional spy of all, was a natural progression. The real language of espionage and the invented language of literary spying are now so entwined that they cannot be untangled.

While spies guard their secrets, they share their vocabularies with remarkable openness. The literary language of spying was even adopted on the other side of the Iron Curtain, where some of Le Carré's inventions are said to have entered KGB parlance. At the same time, Soviet spies developed their own secret language, rich with euphemism: “illness” is Russian spy slang for someone under arrest; “nursemaid” is the term for the security officer accompanying delegations abroad to prevent defections; a “pig” is the term for traitor.

The term “wet job” or “wet work” is often used to refer to an intelligence operation that will involve bloodshed or killing. According to Ames, wet job is “a literal translation of GRU/NKVD (former Soviet intelligence agencies) jargon for ‘killing' - assassination or elimination of people by murder”.

My own favourite intelligence term is “walking the cat back”. This refers to the laborious process of examining past events in the light of present knowledge to establish exactly what happened. The image of someone trying to get a cat to retrace its steps, backwards, precisely captures the problem of reconstructing the slippery essence of espionage.

Spy language is so vivid perhaps because the real business of intelligence, in the testimony of Miss X, “can sometimes be very boring”. In her evidence to the Diana inquest - itself a vast exercise in “walking the cat back” - Miss X described a parallel world of paperwork in another, less colourful spy language: “pink memos”, “white minutes”, cards and indices.

God's access, it seems, can lead a secret agent into the Devil's own filing system.

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