Royal Watch: The final countdown -- six days and counting. Washington may overdose on royalty by the time next weekend's Charles and Diana frenzy is over. Just yesterday, the British Tourist Authority (attracting American tourists to Britain is what this visit is all about) produced a slick 116-page magazine on the "Treasure Houses of Britain" that was inserted into The Washington Post.

In the magazine was "A Royal Message" to those of us here in the lost colonies, signed in blue ink, no less, by Charles and Diana. Unfortunately, in the first sentence, the intrepid travelers made a historical blunder. They wrote: "Two hundred years ago, John Adams, later to be the United States' third president, was appointed Ambassador to the Court of St. James." Any self-respecting Virginian would be quick to leap forward and point out that Thomas Jefferson was the third president; Adams was second. Adams was appointed 200 years ago as the first U.S. "minister" to Britain. The United States didn't send ambassadors until 1893. But then it's tough to keep the history of lost colonies straight. Watt on His Former Colleagues

One thing you can say for former interior secretary James Watt is that either inside or outside the administration, no one can shut him up. Out promoting his new book, "The Courage of a Conservative," Watt said "there's nothing sacred about the Republican Party." In an interview with U.S. News & World Report, he said, "If the Republican Party doesn't become the conservative movement, it'll die -- and it ought to die."

He sees conservatives as the outsiders struggling against "The Establishment that is dominated by liberal philosophy and liberal leaders in every area, including big business and labor, the media, education, entertainment, churches and government . . . By concentrating power in governmental institutions, liberals chisel at the three pillars of society: the family unit, work ethic and faith."

Actor Charlton Heston, who was once directed by Orson Welles in "Touch of Evil," described the late actor/director as "the most talented man I ever worked with -- have ever seen. He was so enormously gifted that things came to him casually." Actress Janet Leigh said, "You left us a lot, I do wish you would have been allowed to leave us more." The two stars were part of an overflow crowd of 500 gathered at the Directors Guild Theater Saturday to memoralize Welles, who died Oct. 10.

But as might have been expected, it was Welles who spoke the best eulogy on Welles. An interview was projected on the screen with him saying: "The trouble with movies today, I think -- and nobody asked me -- is that all of us are too much in love with them. There is no damn cure for it. I would have been much better off after I made my first picture if I'd gone back into the theater, but I had taken the most expensive mistress that any man could have and I've been trying to support her ever since." End Notes

After 39 years the marriage of multimillionaire publisher Malcolm Forbes and his wife Roberta is over. A Jackson, Wyo., judge said Saturday that the divorce was granted in September. They divided up their not unsubstantial property out of court . . .

Senate Majority Leader Robert Dole and violinist Itzhak Perlman will be featured speakers at the black-tie dinner dance tomorrow at the Departmental Auditorium to celebrate the opening of the National Rehabilitation Hospital on the grounds of the Washington Hospital Center. Dole has only partial use of his right arm from a World War II wound and Perlman is a victim of polio . . .

And lest anyone forget the top royal, Queen Elizabeth also has her set of Samsonite and trips about. She returned home yesterday after a four-week Caribbean tour taking in 10 Commonwealth countries . . .

It wasn't there on the surtitles on opening night Saturday of the Washington Opera's "Eugene Onegin." But at dress rehearsal Thursday during the third act party scene a surtitle flashed a quote, "What a feast. Martin Feinstein throws a great party." Feinstein, the general director of the Washington Opera, was sitting in the audience and knew that line wasn't in it. Those opera folks are more fun than they used to be . . .