Britain has sharply rebuked the Soviet Union for the espionage activities of its diplomats accredited to London. The rebuke took the form of the expulsion without detailed explanation of a KGB operative, plus, it seems, a private warning to Moscow that more so-called diplomats will be thrown out if their behavior does not improve.
The incident has made Britain's already cool relations with the Soviet Union even cooler, but the Thatcher government is making efforts to avoid a major confrontation on the spying issue.
The man selected for expulsion was Viktor Lazin, a second secretary who had been watched by the British MI5 counterintelligence service for several months.
All the Foreign Office would say was that Lazin had been asked to leave within seven days because he had engaged in conduct incompatible with his status as a diplomat.
Behind his expulsion lies steadily mounting British annoyance that KGB agents in Britain working under diplomatic cover have been growing bolder and bolder.
Ten years ago Britain, in an unprecedented action, threw out more than 100 Soviet officials, many of them accredited diplomats, accusing them of spying. At that time the Foreign Office reminded the Soviets that there were certain types of intelligence activity that Britain would not tolerate.
It is believed these activities included interference in radical politics, and it seems the Lazin case is connected with infringement of guidelines supposedly adhered toby Britain and the Soviet Union since 1971.
At first it was suggested in Whitehall circles that Lazin had been making direct contact with protest groups in major British cities before and during this summer's rioting. the inference was that he had tried to encourage dissident behavior.
But then the Foreign Office began discouraging the news media from drawing any such conclusion.
Unusually, however, officials refused to give any constructive guidance to reporters.
It seems that Lazin was a member of a KGB section detailed to keep a close watch on left-wing political groups. Some reports have suggested that this section has lately developed unusually close links with certain left-wing politicians in the opposition Labour Party.
A puzzling feature of the Lazin affair has been the Soviet Union's failure at time of writing to retaliate in any way. In the past the Russians have struck back swiftly after expulsions of their diplomats, ordering matching expulsions from Moscow.
The Soviets still maintain a large official presence in London, though it is only about half as big as it was at the time of the mass expulsions 10 years ago.
There are 46 accredited diplomats, plus another 150 officials forming part of trade and other groups. This total is only half that of 1971.
Prime Minister Margaret Thatcher is reluctant to precipitate a crisis in relations between London and Moscow. It would seem she has received US government representations not to take too harsh a line in the wake of the Lazin expulsion.
On the other hand, Mrs. Thatcher has a well-justified reputation as a tough opponent of Soviet communism.
The best explanation of the Lazin affair is that she was angered by the growing openness of Soviet espionage work in Britain and decided to use the Lazin case as an example of what could happen again on a larger scale if the KGB fails from now on to reel in its spying activites in Brita in.