Britain has produced the best-educated spies in the history of international espionage. Many of them spent their youth at Eton College and their early manhood in Cambridge University, where they joined "the Apostles" an exclusive group of aesthetes who believe themselves to be above the normal moral standards expected of ordinary mortals. But unfortunately, they either forgot or wilfullly ignored one line from William Shakespeare. They did not come singly, but in battalions. The problem with British spies is that there have been so many of them.

That is one of the reasons why on July 15, the appearance in court of Geoffrey Prime, a Cheltenham cabdriver, caused such a stir. Prime had been employed for nine years at the Government Communication Headquarters. And although he was not the high-class suspect that British newspapers have come to expect, two other aspects of his prosecution helped to drive the case into the headlines. He was charged under Section 1 of the Official Secrets Act of 1911--the part of the law that deals directly with espionage--rather than Section 2, which catches every loose-lipped crock. And on the day that he stood in the Hereford dock, government press officers actually urged journalists to take the story seriously.

Not that the Whitehall and Westminster press corps need much encouragement to make the most of a spy story. The British class system is a perennial subject of conversation, and the postwar spy scandals have all become enwoven with arguments about the merits of private education, recruitment methods in the Foreign Office and the alleged decadence of the upper classes. John Le Carr,e's high-class spy stories remain compulsory reading for the political establishment. And one award-winning play in London's West End has as its plot the way in which English public schools drive homosexuals into treachery.

Even without this slightly prurient preoccupation, the Cheltenham case, as it will come to be called, would merit careful attention. The GCHQ at Cheltenham is Britain's principal listening post and coordinates the work of other intelligence installations. Whatever information Britain possesses about Warsaw Pact troop movements and the political prospects in the disputed parts of the world passes through Cheltenham. The presence of an enemy agent inside the gates could compromise more than one nation's intelligence-gathering. It could jeopardize the lives of a thousand foreign contacts and open the door into other NATO security systems. Even if the subversive efforts were not successful, the undetected presence of a spy inside a key agency would undermine the confidence of our partners and allies.

And the Government Communications Headquarters is responsible for more security than its name suggests. As well as taking an intelligent interest in the communications systems of other governments, it keeps a watchful eye on what goes on in Britain. A really effective spy inside the organization might well have penetrated the protective cocoon that surrounds British ministers and ministries. Cheltenham is, in every respect, at the center of Britain's intelligence network. When the news of the prosecution broke, members of Parliament were inevitably anxious to hear the government's assessment of its implications. On the first sitting day after Prime appeared in court, the House of Commons was diverted by the news of the intruder in the Queen's bedroom. The next day, the opposition insisted on the prime minister's making a personal statement.

Margaret Thatcher made a brief formal announcement. Prime was awaiting trial. So the sub judice rule either prevented or legitimized her subsequent refusal to fill in any details of the case. But it was clear from each of her terse answers to subsequent questions that she hoped for one clear implication to be read into her replies. The hint was that the worst that could be feared was an individual traitor-- not one culprit from a spy ring with a whole covey of conspirators who had not yet been caught. As is the way with Westminster, the agitation quietly subsided as the MPs awaited both the result of the trial and the report of the Security Commission which the prime minister promised.

But the general unease about security continues. For some of Britain's traitors were more than atom scientists worried about the holocaust they had invented or writers suddenly seduced by the spurious attraction of dialectical materialism. They were ornaments of polite society, high flyers from the ancient universities who might have ridden to the top of the diplomatic corps. One was a courtier, knighted by the queen for the scholarly interest he had taken in her private collection of pictures. When the man in the British street talks about spy scandals it is not usually cabdrivers that he discusses or the noncommissioned officers of the Portland Naval Base conspiracy. It is Philby, Burgess, MacLean and Blunt. Philby once worked inside the Secret Service. He is now a KGB general.

Beleaguered intelligence agencies react to criticism by retreating within themselves and building an ever higher wall around their increasingly secret service. In Britain--still a basically inbred and immobile society-- the idea that national security should be subject to some sort of parliamentary or judicial scrutiny has always been dismissed as radical nonsense. But it is difficult to imagine how confidence can be restored without a major reform in the security organizations. The notion that the procedures for recruitment, vetting and promotion should not be closely guarded mysteries is no longer a matter of civil liberties alone. It is an idea that might just shake the security service out of its old complacency.

And the Cheltenham case is not-- whatever the prime minister may say --the only item on the critics' agenda. The biggest question still to be asked about the security service concerns the invasion of the Falkland Islands. The Argentines assembled a massive invasion fleet, put to sea and landed in Port Stanley before the British Cabinet knew that anything had happened. A Commission of Enquiry now sits to examine how such ignorance was possible. If Thatcher is not convicted of negligence, some blame must lie with this security service.