Oprah prepares for her cowboy showdown

Oprah Winfrey, America's formidable talk-show queen, prepared yesterday for a showdown in court with Texan cattlemen who claim an off- hand remark she made on air about mad cow disease sent the value of beef tumbling.

Jury selection began yesterday in Amarillo, Texas, where Ms Winfrey is expected to testify in court next week. The cattlemen, who are seeking damages to compensate their claimed losses, will rest much of their evidence on the fact that after Ms Winfrey swore off hamburgers during a programme on BSE in April 1996, the value of beef futures on the Chicago exchange fell by one and a half cents. Ms Winfrey's lawyers are expected to testify that the two events were unrelated and that, besides, their client has a right to exercise her right to free speech unhindered by ranchers, meat processors or anyone else.

The very fact that the case is being heard at all testifies to the extraordinary power Ms Winfrey enjoys to influence American opinion. Whether her accusers have any chance of winning the case or whether they will regret having brought it to court at all, drawing unnecessary attention as it does to a bovine problem that has so far seemingly failed to cross the Atlantic, remains to be seen.

What is clear for all to see, however, is that Ms Winfrey's impact on other commercial spheres is enormous. Dubbed "the most powerful woman in America" by Life magazine last year, she has demonstrated time and again that a word of recommendation from her, or even the merest suggestion of approval, can have a mightily beneficial impact on sales of books, records, films and women's clothes.

Her word is gold, in part, because no one can accuse her of having a financial stake in the products she endorses. Worth $414m (pounds 257m), according to Fortune magazine, she is the world's highest-paid entertainer.