June 15, 1986

The first thing that a theatergoer notices at the London theater this season is the empty seats. Although I've sat with my share of sparse audiences over years of London theatergoing, I don't recall ever having previously seen the best-received Royal Shakespeare Company productions play to less than half-occupied houses. This plunge in attendance, attributed to the absence of American visitors, baffles the English. On a local replica of the ''Today'' program one May morning, Albert Finney, the star of the West End ''Orphans,'' rued the fact that ''the cream'' of his play's audience had fled. One could only pity his fellow guest, the American actress Jane Curtin, whose routine promotional interview was soon ambushed by questions asking her to account for the entire falloff in American tourism. But if the ''cream'' of the warm-weather ticket-buying crowds has evaporated in London for now, an English audience does remain. According to The Economist, an astounding one-third of Great Britain's adults see a play or more a year. For both better and worse, that audience seems to be getting a theater that reflects its tastes and self-doubts. The current London season, at least as this observer sampled it night and day for two weeks, reveals a theatrical culture at one with Mrs. Thatcher's majority middle-class constituency.

As Mexico Goes... The secret trip to debt-ridden Mexico taken by Federal Reserve chairman Paul A. Volcker last week underscored the gravity of the latest third-world debt crisis. But this time, the threat to the world financial system is more political than economic, says William R. Cline, senior fellow at the Institute for International Economics in Washington. ''If Mexico wrings big concessions out of its creditor banks or takes radical moves unilaterally,'' said Mr. Cline, ''other Latin American and third-world governments will feel domestic pressure to do the same.'' The reason: Their citizens still resent the burdens imposed by the high amount of interest that must be paid to foreign lenders each year.

CECIL BEATON A Biography. By Hugo Vickers. Illustrated. 656 pp. Boston: Little, Brown & Company. $25. CECIL BEATON, who died six years ago at the age of 76, was an English photographer, set designer, illustrator, portraitist and writer. Critics used to argue over whether he was a true artist in any of these pursuits or merely slick. But on one point everybody, tout le monde, agreed. Cecil Beaton was a great snob. He was not just a big snob but a great snob, an ingenious snob and a daredevil on top of that, a perfect snob and a snob clear through. So much so, that this book by Hugo Vickers, the biographer Beaton chose shortly before he died, turns out to be something Beaton may not have envisioned: an enormous, sloughing, tireless, unsparing, inch-by-inch trench-warfare chronicle of an English snob's progress through the 20th century. Snob is a purely English term. There is no direct translation of the word in any other language. The French were reduced to importing it intact as le snob. Rightly so; le snobisme is a supremely English talent. A snob is someone who judges all things, from shoes and dinner parties to love and beauty, according to their social rating. And there you have Cecil Beaton. This book is not ''Vanity Fair,'' although it is nearly as long, but Beaton is the Becky Sharp of the 20th century.

The last red-and-black truck pulled away from the Ebinger Baking Company's plant in Flatbush on Aug. 27, 1972, leaving thousands of red-eyed customers bereft of blackout cakes and pecan coffee rings. Brooklyn residents viewed Ebinger's bankruptcy as analogous to other borough disasters, such as the flight of the Dodgers and the demise of Ebbets Field.

WITH its newest and most Draconian emergency decree, South Africa seemed to turn a corner last week, abandoning recent efforts to placate hostile outsiders and the restive black majority at home. Instead, as the state-controlled radio put it, the nation's white leaders were braced for ''a showdown with the forces of anarchy and revolution'' - presumably believing that the excision from society of black radical leaders and other activists would stem the angers they sought to articulate. In the mood of crisis and defiance that followed Thursday's decree, and amid mounting pressures from Western supporters, President P. W. Botha declared: ''South Africans will not allow themselves to be humiliated in order to prevent sanctions.'' ''We are not a nation of weaklings,'' he added. ''We do not desire it and we do not seek it, but if we are forced to go it alone, then so be it.'' (Pressure for sanctions, page 2.) The national emergency decree gives the police and army total powers of arrest without charge and search without warrant. Curfews may be ordered. Areas may be sealed off. People who disobey orders of the security forces could, according to the Government Gazette, be shot. The courts may not intervene, and censorship of reporting on anti-Government activism became virtually total. Journalists were forbidden to photograph or make sound recordings of violent protests or the actions of the security forces.