I'll let you into a little secret about all those spies

'Most of their identities are well-known, long since divulged by Russian defectors'

So spies come not singly, but - like troubles - in large battalions. Yesterday the Americans expelled 50 and allowed it to get about that another 400 have probably been involved in espionage. Russians, that is. As with foot-and-mouth outbreaks, there were immediately hundreds of references to the last large-scale slaughter of possibly infected diplomats - Ronald Reagan's 1986 Operation Famish. Which took place, for those without long memories, in the late stages of the old Cold War, when Mikhail Gorbachev was First Secretary. The Russians have already accused the US administration of a historical "relapse".

So spies come not singly, but - like troubles - in large battalions. Yesterday the Americans expelled 50 and allowed it to get about that another 400 have probably been involved in espionage. Russians, that is. As with foot-and-mouth outbreaks, there were immediately hundreds of references to the last large-scale slaughter of possibly infected diplomats - Ronald Reagan's 1986 Operation Famish. Which took place, for those without long memories, in the late stages of the old Cold War, when Mikhail Gorbachev was First Secretary. The Russians have already accused the US administration of a historical "relapse".

Relations are strained. So some questions come quickly to mind. Why so many spies, what with the Iron Curtain rusted away and all? What were they doing? Why expel them now? And, when you get right down to it, who gives a monkey's anyway?

OK, why so many then? The Washington Post, drawing on a seemingly inexhaustible resource of former senior intelligence officers, has been able to calculate that, as the Berlin Wall fell, there were 140 or so KGB and GRU (military intelligence) officers operating in the US. They were disguised as diplomats, trade advisers and journalists at the embassy, the UN in New York and - the most sought-after posting of all, I should imagine - the consulate in San Francisco. With the splintering of the old Soviet Union, that number went down until, by 1993, there were only 100 spooks working for the Russian intelligence service, the SVR.

That seemed logical. But then the number started to grow again. Perhaps Mr Putin et al discovered that there had been a lack of investment in this crucial public service, and decided to reverse the trend. They had certainly discovered that the mere state of being capitalist hadn't suddenly give them the magical technological lift that they had been expecting. Very far from it, in fact. To keep up they'd have to steal. So, said one of The Post's sources, Moscow "shifted into economic espionage, particularly in civilian research and development."

However this begs the question of what use such information would be to the Russians, lacking - as they seem - the enterprises that might be in a position to profit from it. And suppose you do get the blueprint for the latest generation of microchip; the fact is that in two years time it will be obsolete. It is the expertise, the ability to innovate that counts, not the innovation itself.

But there is another explanation, and one that strikes a very human chord. It was offered by "another intelligence specialist" who was quoted as saying that America had attracted the GRU's "best men, because being here is better than being at home" in Muscovy. It is remarkably easy to imagine the inventiveness that such men and women might command to justify a posting in Disneyland.

So there are more spies and they're mostly stealing commercial secrets. Most of their identities are well known, apparently, long since divulged by Russian defectors and a process of elimination from diplomatic lists. But why expel them just now? Well, it seems that they are just taking up too much darn time. A "Bush administration official" spoke of "large numbers" needing to be reduced, "because of the strain it places on US intelligence resources". Thus, just as with the wild deer on Exmoor, the White House had ordered a spy cull before things got out of hand. The implication is that the FBI were happy to chase around after Russkies to a certain extent, but not when it got in the way of other tasks, like spying on Idaho militias or infiltrating the Aryan Brotherhood. So the State Department had requested a "voluntary scaling back", which, regrettably, hadn't happened.

Another possible reason for acting now may have been the recent arrest for treason of the FBI man, Robert Hanssen. Picked up after a classic drop under a footbridge in a park, Hanssen has been accused of working for the Russians for 15 years, of betraying Russians working for the Americans (i.e. of betraying the other side's traitors) and of letting the Russians know about various weird eavesdropping operations being conducted against them. So having allegedly caught a traitor, the FBI must now know many of his contacts (or, at least, it cannot pretend that it doesn't know) and it would seem odd and maladroit not to have them shipped back whence they came.

The final explanation, of course, is that we have a new administration that talks tough, and lots of anxious spooks wishing to justify or increase their budgets, just after another traitor has been unmasked. The combination of the two argues strongly for action.

Now onto the last question: why should any of this concern the rest of us? Isn't all this dead-letter dropping what overgrown schoolboys do to keep themselves amused at our expense?

I have found it hard to take the security services seriously since discovering that, instead of Sir Alec Guinness, Graham Greene and Beryl Reid, their real recent employees have included the likes of David Shayler and Peter Wright. The last expulsion of a Russian spy from America was in 1999, when a Stanislav Borisovich Gusev was caught on camera by the FBI, sitting on a bench outside government offices, monitoring conversations picked up by a bug positioned in one of the building's conference rooms. The bug was such, according to one source, that a schoolboy could have found it.

Let's go back to David Hanssen. He, the FBI alleges, "compromised an entire technical program of enormous value, expense and importance to the US". This is thought to refer to the now famous tunnel burrowed under the Soviet embassy and filled with gizmos, possibly including "tiny microphones inserted in toilets through water pipes to monitor conversations in bathrooms".

Yet (a) the Russians probably knew about it anyway, since - in the words of the defector Stanislav Lunev, a former colonel in Soviet military intelligence, "somebody (in the embassy) dug in the basement with a shovel and found electronic devices, brand new". Meanwhile, pure common sense tells the rest of us to expect tunnels under the Soviet embassy. And, (b), government officials are now letting it be known that nothing of any value was gleaned from the tunnel bugs in any case.

This is the point at which one loses patience. I am all for secret services, accountable to democratically elected politicians. I wish them to have the resources they need to infiltrate and catch terrorists and bombers (though the police seem to manage this pretty well), and to protect us from people who fail to understand that living in a democracy removes any justification for the use of violence. But I am not in favour of the agencies creeping round the world at our expense listening to each other go to the toilet.

As Al Gore put it 18 months ago, silly games go on because "old attitudes in both countries fade away slowly. Sometimes agencies want to use old attitudes as an excuse for old budgets and old personnel rosters. And then the other side has to spend the same amount." Or expel the same number.

David.Aaronovitch@btinternet.com