The duchess and, in a manner of speaking, the duke of Duke Street seem to have gotten their signals crossed.

They have just flown in from London to alert us to the second season of their widely applauded "Masterpiece Theater" series.

But here they are talking up the virtues of "Charlie's Angels," "Starsky and Hutch" and "Kojak," mere specimens of American TV that have crossed the Atlantic in the other direction.

"We can't do that sort of thing at all," says Gemma Jones, who, without her red wig and cockney accent, is a far cry from Louisa Trotter, the scullery maid who gets married so she can have an affair with the prince of Wales and later receives a hotel for services rendered. "American actors," says Jones, "are much, much better at casual reality -- the hip, over-the-shoulder backchat."

A British series called "The Persuaders" was an imitation of "Starsky and Hutch," adds Christopher Cazenove, Jones' co-star, "but not nearly as good." After all, he points out, "'The Duchess of Duke Street' is just a soap opera. It's very well made, but it's a soap opera. It has no more message than "Starsky and Hutch' but it was made with great love."

To further confuse matters, these two reluctant representatives of British-Is-Better have been installed at the Four Seasons Hotel in Georgetown, where the dessert menu includes English trifle and tea is served at midafternoon. Jones and Cazenove have ordered coffee after lunch, but the waiter, recognizing them, comes to ask whether they wouldn't really rather have tea. (They wouldn't.)

It has been two years since Jones and Cazenove finished filming the 32 episodes of "The Duchess of Duke Street." Sixteen of them have aired here, and the second set of 16 begins on Sunday on WETA, Channel 26. While it was a spectacular success at home, making the top three in the British equivalent to the Nielsen ratings, Jones insists that "it's gone in England and more or less forgotten." She can barely remember some of the details of the plot.

Fame, she says, was short-lived. "There were probably a few weeks when I'd be recognized in the supermarket, that's all." Cazenove disagrees: "The memory of 'Duchess' lives on very strongly." Cazenove plays Louisa's tenant-turned-lover-turned-friend.

A successful actress on the English stage -- "I've worked consistently in the theater, but I suppose not too conspicuously from an American point of view" -- Jones was unsure about "Duchess" at first. "My main concern was domestic," she says. "Could I cope with this and [raise her then-18-month-old] child? So I wouldn't have been too disappointed if I hadn't got it."

In Jones' life, as in Louisa's, there was no husband on the scene to help raise her child. But she did nothing so dramatics as Louisa's mysterious trip to have her baby in secret. During the 18 months of work on Duchess," beginning in early 1976, "I had to abandon him a lot," she says, "but I had lots of help."

And there was an artistic fear as well as a domestic one. "I wondered if we might fall on our fannies. I wondered if it might be asking a bit much to have another series [after 'Upstairs, Downstairs," also set in Edwardian times] so soon."

"I was really very dubious," adds Cazenove. "I thought it would be one too many -- but obviously it wasn't."

So why have these two shows -- and others set in the same general period -- been so popular "I suppose," says Jones, "it's near enough to be almost tangible -- our grandparents lived then -- and yet appear to be romantic."

And it's a Cinderella story, "like 'anybody can be president,'" says Cazenove, who spends much of his publicity-related time explaining how to spell and pronounced his name, while -- despite his matinee-idol standing with "Duchess" fans -- disavowing any blood reation to an 18th-Century Italian named Casanova.

Masterpiece Theater runs in the Cazenove family. He has appeared in yet another turn-of-the-century series -- so far unimported -- called "The Regiment." And his wife, Angharad Rees, played Demelza on "Poldark." He also has just been in the London production of a new Alan Ayckbourne comedy, "Joking Apart."

Jones, the granddaughter of a Welsh lead miner (which suits the class origins of her character on "Duchess of Duke Street") and the daughter of an actor, has appeared in four plays since "Duchess," including a production of "Cabaret" in Sheffield. She also did a film of John Whiting's "The Devils," and "I secretly hoped that this might be my big debut, but the spectacle of all those naked nuns pretty well drowned everything else out."

Cazenove says he "fell in love" with Jones in 1963 when he accompanied a busload of fellow drama students to Nottingham to see her in Jean Anouilh's "The Cavern," for which she won the Clarence Derwent Award as best supporting actress.

"When you were just a boy," adds Jones tauntingly.

On their arrival in Washington, the two spent Sunday night in WETA's studios, soliciting contributions and trying "to look as though you're not reading a TelePrompTer when you are," according to Cazenove.

They have tried to resist any detailed explanations of what happens in episodes 17 through 32, beyond the fact that Charlie Tyrrell -- played by Cazenove -- goes off to fight in World War I, while the Bentinck Hotel is bombed and turned into a convalescent home for the war-wounded. And those who are eager to see Louisa and Charlie back together again will not be disppointed.

Jones would like to do another TV show -- "Acting at eight o'clock in the morning I find quite stimulating," she says -- but no more "Duchess of Duke Street." She doesn't want Louisa to wind up covered with latex (for facial wrinkles) and carrying a walking stick.

"The general consensus of opinion was that the second series was superior to the first," she says. On the other hand, "Upstairs, Downstairs," Jones feels, "got quite ridiculous" in its later installments. "If you followed it through literally, the people would be about 100 years old."