The death in Los Angeles two weeks ago of the Grand Old Man of Bridge severed the last link with the founders of contract bridge. Alfred Sheinwold, who was 85, began writing about the game in 1933 and continued to do so all his life in magazines and syndicated newspaper columns. One of his books, ''Five Weeks to Winning Bridge,'' sold millions of copies.

Mr. Sheinwold came to New York City from his native England at the age of 9. By the time he graduated summa cum laude from City College, he was a bridge expert and was immediately hired by Ely Culbertson, the great bridge figure of the day.

In World War II, he served with the Office of Strategic Services, searching out security weaknesses in military establishments around the world. His later bridge career included service as chairman of the National Laws Commission and editor of the American Contract Bridge League's Bulletin. The Kaplan-Sheinwold system he developed with Edgar Kaplan was important to the theory of the game and is still widely played.

Although his busy schedule left him few opportunities for competition, Mr. Sheinwold was a fine player who captured two national titles and many lesser ones. On the diagramed deal, played in 1958, he held the East cards and defended four hearts after opening one spade.

He won the opening spade lead with the ace and returned the suit. South won with the king and cashed the king and ace of diamonds. He ruffed the third round with the jack, and Mr. Sheinwold made the key play: He refused to overruff and threw a club. Now he could not be prevented from taking three trump tricks to defeat the contract.

A much less obvious line of play would have succeeded for South. If he had immediately played the heart ace and followed with the jack, he would have been able to draw trumps. He would then have made a tenth trick, either by establishing dummy's clubs or by squeezing West in the minor suits.