The result is the naming of spies - 87-year-old Melita Norwood is not the first elderly ex-agent to take a bow in recent years and she will not be the last. But how important a spy was she? Commentators compare her treachery to the level of Burgess, Maclean, Philby, Blunt and Cairncross, known in the trade as the Magnificent Five. Mrs Norwood, they say, is the magnificent sixth. I find that estimation of her standing very hard to accept.
Mrs Norwood was an employee, and not a senior one, of a body called the British Non-Ferrous Metals Research Association, which carried out contract work for departments of the British Government engaged in wartime and post-war work on nuclear weapons and nuclear energy. She was at the periphery, rather than the hub of this work.
Donald Maclean and John Cairncross, to take just two, were very close to the hub. They were senior public servants who either witnessed or participated in key events and had access to core documents. It is difficult to see how Mrs Norwood's espionage contribution could rank with theirs.
Still less can it rank with the work of two spies not listed among the "Magnificent Five" - Klaus Fuchs and Ted Hall. Both were extremely able scientists at the cutting edge of A-bomb development in wartime Los Alamos, who provided the Soviet Union with rich seams of documentation and analysis on the vital challenges of the weapon. Is it possible that Mrs Norwood's espionage rivalled his? In a word, no.
This is not to say that the uncovering of Mrs Norwood is not a scoop - merely to find her alive and prepared to defend her actions makes it a compelling story. However, it does not alter our historical understanding of the early nuclear arms race, nor does it much affect our grasp of the spy race.
We have known for some years that Soviet intelligence penetrated Western society and governments on an awesome scale - on a scale, indeed, that begins to rival what Joseph McCarthy warned of. The release to the public of a large archive of documents known collectively as Venona taught us that.
Venona comprises secret Soviet wartime messages that were intercepted and partially decoded by the Americans and the British. The decoding began in the late Forties and led in its early stages to the unmasking of agents such as Maclean, Fuchs and the Rosenbergs. The messages left no doubt that there were literally hundreds of Soviet agents in the West.
Venona, however, posed a problem, and that problem grew in importance as the years passed. Because only fragments of the traffic could ever be decoded, and because the contents were almost always cryptic (cover- names were used, for example), the effect on the official spycatchers was tantalising, almost maddening. They spent decades struggling, usually in vain, to puzzle out the identities of agents, many of whom were mentioned only in passing in the KGB messages. In time they fell into a mood of paranoia that is so well described in Peter Wright's Spycatcher.
Now that the Venona material is in the public domain - you may read the original documents on the website of the US National Security Agency - we can all play the puzzle game. One consequence was the unmasking of Ted Hall, the American atomic spy now living in retirement in Cambridge. There have been others in the US and there will be more, both there and here.
But there is a catch, for we can get it wrong. The agent now revealed to be Mrs Norwood figures briefly in Venona as "Tina", but no less a writer than Nigel West had previously linked "Tina" with someone completely different - the late Lady Eugenia Peierls, wife of a distinguished nuclear scientist. West's suggestion was hotly disputed by her family; they now seem vindicated.
We can also get it wrong in other ways, by overestimating the degree to which someone identified through Venona was a knowing agent, rather than a passive source of information, or by misreading the significance of their espionage.
As book follows book in this season of spies, it would be as well to remember the first lesson learned by the spies themselves: take nothing at face value.
The writer's book `Test of Greatness: Britain's Struggle for the Atom Bomb' is published by John MurrayReuse content