Susan Hampshire is queen of the British literary soaps, a position that differs from being queen of plain soap opera in that:

Her fan mail comes addressed to her, not to Fleur Forsythe, the character she played on "The Forsythe Saga" television series, or to Lady Glencora Palliser, as whom she is appearing on "The Pallisers," now showing Monday nights on WETA (Channel 26).

She can fill a London theater for a classical play, while the stars of "Upstairs, Downstairs," which has no literary affiliation, can only fill a theater outside of a London and with "a commercial play," she has noticed.

People who resent the behavior of a character she plays don't walk up and slap her, as has happened to more than one American soap star, but discuss it in a civilized way, referring to the truant in the third person.

When she wants her role changed or enlarged, she comes armed not with threats from an agent, but with supporting evidence from a deceased novelist.

Instead of talking about being stuck in a long-term television role and wanting to get back to the theater and do other things, she speaks of "the luxury of being able to develop a character at length," and does do other roles in the theater - Shakespeare, Shaw, Barrie, Maugham, Strindberg and Anouilh alone, in the 2 1/2 years since the Palliser programs were filmed.

A class operation, obviously.

And so is the personal revelation part of the American promotion tour for "The Palliser" series which she concluded in Washington yesterday, with interviews and a party in the Kennedy Center by "The Palliser" sponsors, Prudential Insurance.

"Probably I'm a happy person because I'm rather dull," she said, in what is not the usual opening gambit of a swingy-looking blonde star, preparing to confide all, in a Watergate Hotel suite, for public consumption.

"Dullness" turns out to be an interest in work, one's duty to humanity, family life and fidelity in love. Matters often neglected in modern novels - let alone publicity-talk - in favor of racier stuff, but important in Victorian novels, which may account for their revival of popularity as experienced by the television dramatizations.

"Perhaps that's what people crave now," she said. "The lack of it hasn't particularly worked, has it? You know, they say that people in Sweden commit suicide because of those long winters - but what about all that freedom they have?"

One of the things she admires most in Lady Glencora, a woman who makes a success out of a marriage she felt forced into, is "her steadfastness, her strength of character. She could have gone around having lots of affairs, but she didn't.

"I admire fidelity enormously. A really good relationship thrives through fidelity - you're either with someone or you're not. When I was married, I was happy, but that was only because I knew nothing about what my husband was doing." When she found out, she got divorced.

Her own parents, a scientist and a ballet teacher, were separated all her life - she, in fact, was the result of an attempt to reunite them. "My father had a first-class ticket on a ship and my mother got a tourist one, and when he entered his cabin, there she was. When he got off the ship, he went his own way. So she didn't get him back with this, but she got me."

Asked her age, she replied: "I always lie about my age. What age would you like me to say?"

Hampshire describes her one-parent and three-sibling family as "very jolly," and herself as "resiliant."

When she was unable to fill her "passionate desire to become a nurse" because of dyslexia - an ailment which still makes her have to put in "five times the amount of studying time" on a part than an actress normally would - she decided to become an actress. When she couldn't get a job as an actress, in spite of having made two films at the age of 5 after being "discovered" on a subway ride, she got a job in the theater "making the tea and sweeping the stage."

Early rejections (partly because she was physically unable to read a part on sight) and self-evaluated incompetence ("I was so dreadful, people would come back to see what dreadful thing I'd do next") didn't deter her.

And such personal difficulties as four miscarriages and one stillbirth, and her divorce didn't leave her "sitting around weeping."

When she speaks of problems which have bothered her, they are quite different.

In the mid-'60s, when she was first successful in films and plays, it was feeling "that I was being paid a lot, and not giving value for money." In the course of worrying that she ought to be doing something more useful, such as teaching, she impulsively flew to Africa to talk things over with Dr. Albert Schweitzer.

The problem has been solved, she said, by having met people whose sole joy in life is from entertainment such as she can provide, from the fact that "the government takes three-quarters of your money now, anyway," and from having a 5-year-old son to provide for.

Another thing that bothers her is the people who write letters, in which they keep using her name, "Oh, Susan, how are you, Susan, how is your son, Susan, I heard you had a cold, Susan."

"I know they write to everyone," she said, "but I answer them because that letter may be the only letter in their box this week, and television may be their only friend." The risque ones might say "'Send me a picture of you in your knickers and bra' - if I have a '60s picture of me in a swimsuit, I send it. Why not?"

She feels strongly about "the criminality" of letting children watch television constantly, and says she tries to offer her son "a vital home life, instead of a box." And her idea of "monstrous" is being told she could not adopt problem 3 year olds because she was a working mother.

"Duty - duty is actually a pleasure to me," she said. No Victorian lady could have made such a shameless statement.