In Dead Drop, I took a fresh look at one of the most famous spies of the Cold War, Oleg Penkovsky. A colonel in the GRU, Soviet military intelligence, in 1960 Penkovsky volunteered to spy for the West and was eventually ‘run’ jointly by MI6 and the CIA. He provided crucial information to the West, including manuals that helped identify the missiles Khrushchev had placed on Cuba. The CIA’s senior analyst Ray Cline told historian Christopher Andrew that Penkovsky’s intelligence was vital to the resolution of the Cuban Missile Crisis, as it allowed the agency to ‘follow the progress of Soviet missile emplacement in Cuba by the hour’.

The CIA’s involvement in the operation made my research a lot easier, because in 1992 they declassified a vast amount of material about it, including all of the transcripts of the meetings they and their British colleagues had had with Penkovsky, albeit with some redactions. I read over 1,400 pages of raw material during my research.

MI6 take a very different view to this process. Not only have they never declassified a single document about the operation, they even (indirectly) asked that I remove several pieces of information from the book, including some that was already firmly established in the public domain. In one case, the information featured in an obituary that had been published in The Times, while in another it was in an entry on Wikipedia.

So there are still holes in our knowledge of this operation, despite it taking place over half a century ago. The same applies, of course, to many other operations and aspects of the Cold War. But some of these holes are, slowly, being filled in. Last month the CIA declassified a new tranche of documents, including a couple that relate to Penkovsky.

One is written by Leonard McCoy, the brilliant CIA reports and requirements officer who worked on the operation, and who I was lucky enough to interview for Dead Drop. His article – undated but judging by one comment probably from the 1980s – adds little new, but fleshes out a few tradecraft details and makes it clear how valuable agent HERO was to the CIA. McCoy concludes that the Russians most likely realized that Penkovsky was betraying them thanks to information from two double agents, William Whalen and Jack Dunlap. He also notes that the CIA’s fondness for camouflage and deception operations during the latter part of the Cold War was triggered by a Soviet intelligence manual on the subject they had been passed by Penkovsky.

The other document the CIA has declassified about the operation is ‘Reflections on Handling Oleg Penkovsky’. Also undated, this looks to be a much newer document, probably from 2011. It includes an interview with Rodney Carlson, who as a junior CIA officer had worked on the operation.

Carlson’s name is, absurdly, also redacted from the interview, even though the first footnote in the document refers to a book that discusses him by name in relation to a meeting he had with Penkovsky in the American ambassador’s residency in Moscow on July 1962 – which he also discusses in the interview. So, as with MI6 and Wikipedia entries, caution over which secrets to reveal can seem frustratingly arbitrary.

Nevertheless, the unredacted content of the document makes it clear it is Carlson being interviewed, and his recollections of the events even five decades on are revealing.

The first revelation is a general one: we get a clear sense of his personality, I think for the first time in public. He is sharp, astute, and like McCoy has an exceptional recall of the operation. His role in it remains unchanged, but the effect is rather like hearing an extra speak in a cut scene from a film – suddenly, we see an unexpected and slightly different angle on events.

Intriguingly, Carlson points to an anomaly in a statement by a KGB officer made to the author Jerrold Schecter in 1990. While the Russians have always insisted that Penkovsky was initially detected by routine surveillance, one KGB officer told Schecter that the way he had been caught still couldn’t be revealed. ‘That suggests there was more to Penkovsky’s compromise,’ Carlson said, ‘probably a lot more, than a suspicious sighting during routine surveillance’.

The current consensus in the West is that the Russian story of routine surveillance is correct. Someone who disagreed was the late Pete Bagley, a CIA officer who had reviewed the Penkovsky operation and who I interviewed for Dead Drop. He made the same point as Carlson, hitting on precisely the same anomaly, in his book Spy Wars, and it was the starting point for my research. Leonard McCoy had been more coy on this point and is in his article. Others have pointed to Whalen and Dunlap as being possible instigators of a chase for Penkovsky, but his wording also doesn’t suggest someone who necessarily believes the KGB line, either. 

In Dead Drop, I discuss at length the possibility that there was indeed ‘a lot more’ to Penkovsky’s detection than the KGB’s story of how it happened, and present what I think is the most likely scenario. But it’s fascinating to learn that at least one CIA officer who was involved in the operation felt the same as recently as (it seems) 2011. It might simply be that Carlson read Bagley’s book and found the anomaly convincing, but even that is interesting, as many in the CIA were very much against Bagley's book and his approach, among them Leonard McCoy.

A huge amount is known about the Penkovsky operation, and I hope with Dead Drop to have written as close to a definitive history of it as I could. But one can always learn more. Both these newly declassified documents contain snippets of new information, even if only of texture, as well as some curious omissions – the interview with Carlson has nearly two full pages redacted – despite the fact that these events took place in the early Sixties.

MI6 has yet to declassify its side of the operation, as have the KGB and the GRU. So it might be decades before the complete story is known, if then. Espionage history, perhaps even more than other branches of history, arrives in a slow drip.