When I confronted "Smith", a crumpled, middle-aged man, he twisted and turned, saying that he had talked to the Stasi only about general social and political issues, not individuals (which, I know from his own informer's file, was untrue). The trouble with Communist states, he said, was that they lacked a "civil society framework"; by informing, he was trying to make up for that. A wonderful rationalisation. But he also explained - truthfully - how he had been cleverly blackmailed into working for the Stasi.
Now we in Britain are getting a taste of what Germany has been through for the last decade. The opening of the Stasi files, together with the remarkable new material from the KGB archives, means that former agents and informers are sensationally exposed to public scrutiny. In Germany, they call it "outing".
I feel repugnance at what Robin Pearson did: betraying the trust of colleagues, and (according to BBC2's The Spying Game) proposing to set up a further British-East-German student exchange so that more young innocents could be entrapped. Yet on all the evidence, he did little serious harm to Britain. As with so much top secret material in Soviet bloc archives, most of it you could have found in our newspapers. For example, the fact that the exiled Polish professor, Zygmunt Bauman, on whom Pearson reported, was a stalwart supporter of Solidarity, was hardly news to anyone who followed Poland at the time.
To be publicly shamed seems to me sufficient punishment for such a small- time agent - and perhaps even too much punishment for his wife and family. When I wrote about my experience in The File, I deliberately left those who had informed on me with the threadbare cloak of their code-names. Sensationalist "outing", in which the journalist's proud claim of "public interest" often means little more than "what interests the public and, therefore, sells more copies", seems to me itself morally questionable.
After more than a week of media spying frenzy, it's worth stepping back to reflect on what we've learnt - and what we should really be asking now. We've been reminded that reading about spying is a great British hobby, second only to gardening. It's somehow typical that the BBC series is called The Spying Game. Not quite cricket, but still. Then we've been reminded that there were a lot of spies in Britain even in the last years of the Cold War. And it's useful to recall that serious people could still think East Germany was a better society than ours, just a few years before the Berlin Wall came down.
But the quality of the information gained by these spies is hardly impressive - not a patch on Philby, Burgess and Maclean. Pearson could inform the Stasi in depth about his speciality: fire insurance in the industrial revolution. But serious state secrets? The Stasi files are full of such Pooterish material. My informer "Smith", for example, contributed hand- drawn maps of the British Council offices in West Berlin and London. Hot stuff.
You may say: surely the big fish are still to be found? Well, perhaps. But while many of the Stasi foreign intelligence files were spirited away, most of their agents seem to have been identified. And the KGB materials carefully noted by Vasili Mitrokhin really do constitute a remarkable record of their spying abroad. The historian Christopher Andrew, in his account The Mitrokhin Archive (Penguin Press), concludes that Britain had much the better of the spying contest with the Soviet Union in the Seventies and Eighties, whereas the Communists had won hands down in the Thirties and Forties. For all the advantages enjoyed by a closed society spying on an open one, they were losing the secret war before they finally lost the Cold War. We had bigger fish in their pond than they had in ours.
The real horror of the Stasi, as of the KGB, was the way they spied on their own people, not on us. That persisted, in Orwellian dimensions, until the bitter end. This is the truly poisonous legacy, which I have been exploring in a new series for BBC2, Freedom's Battle. Germany has been wrestling with the legacy for 10 years; we are lucky enough to have just about enough for 10 days. But, beyond this, I also try to explore what seems to me the most important question, curiously unasked in the coverage thus far: who is spying on us now?
Well, of course, the foreign intelligence successor to the KGB, the SVR, is still spying on us, together with a clutch of unfriendly states - and doubtless a few friendly ones too. The human techniques they use, exploiting vanity, greed, sex and misplaced idealism, are as old as Methuselah. But, and this is an important point, the technological possibilities of electronic surveillance are spectacularly better than ever before. You can now secretly watch and listen to almost anyone almost anywhere. Then, in a different category, a few of us will be watched by MI5 and listened to by GCHQ in Cheltenham. Another lesson is that we have to keep watching our own watchers, especially because of the enhanced technical possibilities for snooping. (Do we feel that the head prefect Tom King and his committee have the appetite and teeth for that job? We doubt it.)
Yet I think the most characteristic and worrying development of the post- Cold-War world is the growth of what might be called private or free enterprise spying. Typically, when we tracked down former secret policemen in Berlin and Prague for our series, we found them working in private security firms. Increasingly, our lives are covertly intruded upon not by the agents of states, but by private agents: employers, insurance companies, credit operators and, yes, the media.
We could see Robin Pearson on our television screens on Sunday night because the BBC reporter used a spy camera, hidden in his tie, to film him. There's a poetic justice in spy methods being turned against the spy. But, all too often, the paparazzi and the tabloids use the techniques of spying to intrude upon private lives when there is no possible justification of public interest. Then it was the Stasi, now it's The Sun.
The author's book `The File' is available in paperback from Flamingo. The first episode of `Freedom's Battle' is on BBC2 at 8pm on Sunday 31 October. `The Spying Game' continues on BBC2 on Sundays at 8pm