The British have a useful word, ''yob,'' which the dictionary defines as an ''uncouth, ignorant, loutish youth.'' The word is traditionally applied to males, but in these liberated times can also refer to females, and might have been in use last week at Buckingham Palace when Barbara Bush, the president's daughter, appeared for lunch wearing denims. But of course I'm talking about the president's daughter. The other Barbara Bush, the president's mother, would sooner appear in a wet T-shirt contest at Hooters than wear jeans to lunch with the queen.

There was a time in living memory when no one needed to be told that you should dress up when invited for lunch at Buckingham Palace. Of course, the younger Barbara was not exactly invited to lunch at the palace. She decided to come ''on a last-minute whim,'' according to the Times of London. Perhaps that means she brought along nothing else to wear.

It is not uncommon for American students to visit Europe with three clothing items jammed in a backpack, but then again, they mostly dine at McDonald's. In a similar situation, invited to lunch with the queen, every woman I have ever met in my entire life would have cried: ''I don't have anything to wear!''

But perhaps denims are Barbara's native garb. It is perfectly appropriate for a Japanese woman to wear a kimono to the palace, or an Indian a sari. Perhaps Texans wear jeans as their traditional costume. Using the same loophole, she could have added a Dale Earnhardt T-shirt.

At the palace, which has had yobs even in the royal family (the duke of Windsor comes to mind), Barbara's unexpected appearance was greeted unflappably. She was not invited to dine in the 1844 Room with the queen and the duke, but sent ''below the salt'' to the Billiard Room, with the master of the household and other lesser dignitaries.

Meanwhile, her father was having his own difficulties, appearing at lunch with a wet suit and shoes after being drenched in a sudden shower. That the president of the United States cannot get himself from his bulletproof Cadillac limousine to lunch with the queen without being caught in the rain is perhaps an insight into his need for a missile shield.

Barbara's grandparents, so much more widely traveled than the president, no doubt cringed with embarrassment that their grandchild turned up at the palace in jeans. Did Barbara's father and mother speak with her about her fashion sense? This is, I realize, a ''family matter,'' but yob culture begins at home.

George W. Bush was so indifferent to the world that in the years before he became president he made only two overseas trips, both for business, neither for curiosity. No wonder he wants to beak the missile treaty, alienate NATO, ignore global warming and reinstall Russia and China as enemies: Those foreign countries scarcely exist in his imagination. Why go to Australia when you have the Outback Steakhouse right here at home?

Our previous president studied at Oxford. This one was given a sightseeing tour of London and said it was ''diverse and clean.'' The Times also said Bush gave a ''pep talk'' to children about the advantages of reading over television. The children did not ask him to name the last book he had read. Just good manners, I guess.

-Roger Ebert