Bernd is heavily built and sweaty, the Stasi having seen fit not to supply me with the more sensual temptation of a well-toned Romeo agent. After a lot of talk about what I have learnt of life under "socialism as it really exists" during my stay, he asks whether there is anything "we" can do for me. "Well," I say, "it is always difficult getting a visa and I'd like to come to East Germany once a year or so, in order that I might keep up with friends and developments. Could you sort that out for me?"
"In that case," says Bernd, "we have a proposal. My friend Georg, the one you met when we went to visit ADN [the East German news agency], can find you a flat here. You'd have a base to come and go and do your research." In return, he suggests, I could monitor the Western press for ADN. Of course, it would be "interesting" if I could also use my "analytical abilities" more broadly, to assess geo-political developments, and there are a lot of ways this could be arranged - by keeping in touch from home, going to international conferences (particularly those on disarmament) and writing reports on the state of public opinion.
At no point did Bernd use the words "spy", "Stasi" or "informant".
Years later, when I was co-authoring the memoirs of Markus Wolf, the former head of East German intelligence explained why: "A major factor is the erotic appeal of the East; the prickly excitement people felt at being feted and taken seriously on the other side of the Iron Curtain, and the forbidden excitement of it all. It was best to allow a certain moral ambiguity to thrive about the purpose of a recruitment."
At the same time that I was turning down Bernd's offer of a "des res" in East Berlin, we now learn from the Mitrokhin files, another student, Fiona Houlding, was recruited in Leipzig under the code-name Diana, using the same ploy of an ADN contact. She agreed to help monitor the activities of the far right in Britain and took some money from the service. Robin Pearson, the Hull lecturer, went further, agreeing to inform on colleagues, as did Gwyneth Edwards at Loughborough.
They said "yes" to their Bernds for all sorts of reasons: ideological sympathy and money are the factors emphasised today. But the more common motive was the frisson that harbouring a big secret brings. There you are, labouring away on a research topic which interests about three other people worldwide (mine was "The Search for Subjective Authenticity in the novels and literary theory of Christa Wolf" - you see what I mean), an insignificant cog in the wheels of academe, completely irrelevant to the wider world.
But you hug to yourself the knowledge of being more discerning than the other library drones. You, after all, have been specially chosen to fight on the invisible front of the Cold War. The ideological enemy of your own state thinks you are valuable - worth rewarding with holidays and dinners, if you are squeamish about taking cash. You are a person of some importance.
The classic defence of informants is that they did not do anyone harm. That will not do. They were not in a position to know whether they were doing harm or not. Anyone who denounced a fellow Briton in East Germany condemned that person to the attentions of the Staatsicherheit and thus invaded their privacy. Far worse, they also steered the attention of the Stasi towards a target's friends and acquaintances in the East, with far worse potential consequences.
But the Mitrokhin files will not only embarrass those named in them. They may prove to be the last booby trap of the Cold War, its wires left lying around in the debris of the ideological conflict to trip up the unwary.
One fact that has been overlooked so far is that it is MI6, with or without the support of MI5, which has released this information into the public domain, albeit by proxy. The secret service, which is fond of reminding us that it cannot be rendered too open since that would stop it being effective, chose to betray its own classified information. Mitrokhin collaborated with Christopher Andrew, a historian trusted by MI6. The information would not have become public unless the intelligence elite had wanted it that way. Why?
Since the acquittal in 1991 of Pat Pottle and Michael Randle - the peace activists who helped the infamous George Blake to escape to Moscow - MI5 has given up on bothering to try to secure prosecutions. On the other hand, it could not bear to let people such as CND's Vic Allen and Tribune's Richard Clements off scot-free. These people were the enemies of the British security services in the hard-fought battle for public hearts and minds over nuclear disarmament in the Eighties. Now they are being punished by public exposure.
In so doing, however, the gentlemen south of the Thames failed to consult the Government and made a mockery of the Intelligence and Security Committee, which supposedly monitors their activities. They have allowed a precedent to emerge in which copyright of intelligence material is given away solely at the discretion of the secret services, to the profit of individuals.
Yesterday Oleg Gordievsky, the Soviet defector, argued in The Sunday Telegraph that MI5 and MI6 "do not have the power to authorise the prosecution of anyone. Nor does the Home Secretary". Up to a point, Oleg. If the intelligence services are convinced that there is strong evidence of espionage by a British national and seek a prosecution, they certainly do have ways of achieving that goal. I know of one woman, a former MoD employee suspected of being recruited by an East German Romeo, who was subjected to rigorous questioning over months in an attempt to secure a confession until the matter was abruptly dropped with no explanation. The real problem is that the guidelines for investigation, let alone prosecution, are so unclear.
Mr Gordievsky is now the nearest thing MI6 has to an official spokesman, pumping out the official line on what the British intelligence service does and doesn't, can and can't do. That is a role that should more properly be filled by David Spedding, the director general of MI6, and Stephen Lander at MI5. They are using proxies instead of speaking with their own voice. That must change.
Wholly by accident, the Mitrokhin affair may boost the cause of greater accountability. By exposing how little insight, let alone influence, the Home Secretary and the monitoring committee have over the strategic decisions and procedures of the services, the men from the Albert Embankment have reminded us of the importance of the oldest question in a democracy: "Quis custodiet ipses custodes?"
It is not a service that this particular bunch of custodians intended to perform for us when all this started, but it's welcome for all that.