There is a tendency to regard the expulsions of all those diplomats and other personnel by Britain and the Soviet Union as a kind of tit-for-tat game that sophisticated nations play. A "score" is kept -- currently it's 31-31 -- and similar motivations of stubbornness and pride are attributed to both sides. At the same time, explicitly in Moscow, implicitly and quite widely in the West, a certain onus is put on London for overreacting and expelling the 31 spies fingered by the defecting KGB London station chief. It is said that the train of expulsions thus begun may have damaged relations.

But let us not forget where this train left the station. It was at Espionage Central, the typically large, hostile and intrusive extravaganza that the Soviets mount wherever they can. A government that was presented with formidable evidence of a huge spy nest and did not act would not deserve to hold office. Prime Minister Margaret Thatcher had it exactly right when she said, "We have eliminated the core of their subversive and intelligence operation in Britain." This is what is called the national interest. Categorization of the episode as a 31-31 "draw" in expulsions trivializes this central fact.

East-West relations have built into them a certain tolerance for mutual espionage, one of its purposes being to minimize surprises. But the Soviets, working arrogantly in open societies, go too far. It is the outlandish size and intrusiveness of their espionage program in Britain, not the uncovering and the undoing of it, that assaults the principle of good relations. To put even a slight burden on the British is to turn the equities upside down. For the Soviets, good relations mean a condition in which they can practice espionage with minimal restraint. Bad relations is a pejorative term they wield against a Western government ready to challenge their audacity.

Receiving Mikhail Gorbachev, Margaret Thatcher said he was a man Britain could "do business with." She meant, it seems, commercial business and general diplomatic business, and perhaps she'll turn out to be right. The best way to "do business" with Mr. Gorbachev, however, is to do hard things when you have to do them. Mrs. Thatcher did just that when she cracked down on the KGB.