It’s been quite a week for Jeremy Corbyn. After allegations by retired Czech spy Jan Sarkocy that the Labour leader was a paid informant, Conservative politicians doubled down, with defence secretary Gavin Williamson describing it as “a betrayal of this country,” and security minister Ben Wallace likening Corbyn to British defector Kim Philby. All allegations have been rebutted by Labour and it appears that Sarkocy is a fantasist and that Corbyn was not considered a spy by either the Czech or the East German intelligence organisations.

But amidst the claim and counter-claim, what is actually meant by the terms spy, agent, informant and contact? Was Corbyn “naïve” to have met foreign diplomats? Did he betray his country or undermine British security by doing so?

It is not difficult to find out how intelligence agencies manage the recruitment of their sources: the CIA has articles on its website, former intelligence officers have written about their craft and there are films and lectures available online. In the world of human intelligence (known in the trade as HUMINT) there are three basic categories of person: the intelligence officer, the agent and the target. The intelligence officer is a staff member of an intelligence agency, such as the CIA, MI6 or, in the case of Sarkocy, the Czech StB. An intelligence officer is sometimes known as a spymaster but is not a spy. An intelligence officer’s job is to recruit and “run” (manage) spies.

Spies are also known as agents, informants and sources. The key definition of a spy is that they have been recruited. This means that they have been asked to provide secret information by the intelligence officer and knowingly agreed to do so. Spies’ motivations vary: the CIA typically viewed its recruitments as relying on a combination of “MICE” – Money, Ideology, Compromise, and Ego.

A target is someone who has been ‘spotted’ by an intelligence officer as a potential recruit. Officers will assess whether their target has access to secret information, whether they have the motivation (the MICE factors) and whether they are suited to being recruited (for example, a notorious drunkard incapable of keeping secrets might be judged unsuitable).

Take a real-world example: Kim Philby was in a senior role inside British intelligence and responsible for passing huge quantities of damaging intelligence to the Russians. Philby led a chaotic personal life, but his ability to evade capture over a forty-year double life demonstrates his suitability as an agent. His access to secret information at MI6 was not in doubt. His motivation, clearly expressed at various points after his flight to Moscow, was a long-held belief in Communism.

Since the claims against Corbyn appear not have any basis in fact, we cannot analyse his “case”. But we can indulge in a thought experiment: if we were Cold War-era intelligence officers from an Eastern Bloc country seeking to find out secrets about how Britain was run, would we target Corbyn? What might, in this theoretical case, Corbyn’s motivations be? Looking at the MICE framework leaves slim pickings: there is no evidence that Corbyn is very interested in money and he appears not to have much of an ego. Extensive attempts to compromise him by drawing attention to some of his controversial relationships have failed. This leaves ideology as the only recruitment peg in this entirely theoretical targeting exercise: his strong left-wing views might incline him to respond positively to an Eastern bloc recruitment pitch, although he has vehemently denied this.

Just supposing that Corbyn had been targeted, what access did he have, in the 1980s, to classified information? Famously, until his election as Labour leader, Corbyn never held any shadow cabinet (still less government) post. Until his election as leader, Corbyn has always been viewed as a fringe figure in Labour circles. It is therefore hard to believe that he had any access to classified information at a time when he was regarded by the British establishment as a subversive figure. He certainly wouldn’t have known what Margaret Thatcher had for breakfast.

What is not in doubt is that Corbyn met a Czech diplomat who was subsequently revealed to be an intelligence officer. This suggests that, for Sarkocy at least, Corbyn was considered a target. There is no evidence that he was recruited. Therefore Corbyn would not have known he was meeting an intelligence officer. Was Corbyn wrong to have met a foreign diplomat? If he was, many hundreds of other politicians have made the same error. Stalin’s ambassador to Britain in the 1930s and 40s records numerous meetings with prominent politicians of all political colours in his diaries. Ignorance seems a reasonable defence when meeting a foreign intelligence operative; it is one used by Boris Johnson, after all.

Arthur Snell is a former diplomat who works as an intelligence and security adviser