Diana Rigg arrived on American television in 1966 as long-legged, jumpsuited Emma Peel, specialist in karate chops and swift kicks and partner of Jonathan Steed (Patrick Macnee). Together they were known as "The Avengers."

Beautiful, steely and forceful, she followed Honor Blackman, who originated the role in Britain, and was an instant hit. But for a young woman trained in classic theater, the series was merely a diversion.

Shortly afterward, she joined the British National Theatre headed by Sir Laurence Olivier, who called her "a brilliantly skilled and delicious actress." A critic gushed that she was "England's emergent superstar."

Today, Diana Rigg is 52, still lithe and assertive, but American television audiences see her rarely. For a few moments each week, she turns up in her second season as the genteel host of PBS' "Mystery!" (Thursdays at 9).

Ten days ago, she accepted from Princess Margaret a citation from the British Crime Writers Association honoring the series and its funder, Mobil Corporation, for "10 successful years."

But since the birth of her daughter Rachel, now 13, Diana Rigg has developed strong views about television content. She believes that parents need to take a close look at what their children want to watch.

"Television has the power to influence for good -- a great deal of good -- and also has the power to influence for not so good," she said.

"I think it's unfortunate that the bias is largely toward the latter, and that because the majority of people like to sit in front of the television and be anesthetized in one way and another, they aren't given good programs that teach and inspire. Commercial companies play to the lowest common denominator, and I think it's very sad that it happens that way."

Rigg is not afraid to forbid her daughter from watching shows she deems unsuitable. She once stood alone among Rachel's friends' parents in telling her she could not watch a British series called "Grange Hill," about a school in which, Rigg said, "The teachers behaved appallingly, the children behaved appallingly toward the teachers, the children behaved appallingly toward each other, and I thought it was repulsive. All her class watched it. I was extremely unpopular. But I don't care. I hated the idea. I gave orders that the nanny wasn't allowed to switch it on.

"The power of television, manipulating my child. I was bringing her up with one set of standards and the television was teaching her another. That's where parents must say, 'No, I disapprove.'"

On the other hand, she acknowledges that there are programs worth watching and she believes that "it's absolutely vital that an alternative channel exists that at least keeps some standards flying."

She said she's looking forward to seeing Ken Burns' "The Civil War" on British television, and she enjoys "Cheers," calling the sitcom "a very good program of its kind. I think it is a very high standard format-show. I wouldn't quibble about that being shown on English television at all."

But much of what is shown both there and here is what Rigg called "rubbish," programming that airs largely because "people have been brought up not to expect better of television."

Chatting over coffee at her suite in the Grand Hotel here, Rigg appeared concerned about the British Broadcasting Company, long the source of much programming for the United States' Public Broadcasting System.

The BBC, she said, "is gradually being squeezed, and I think the standards at the BBC are going to fall dramatically. They're into sort of franchising and playing the demographics."

Like many actors, even those who appear on the tube, Rigg watches little television at home.

"I tend to watch the good, much as you'd pick up a book to read or you'd go out to see a particular film. That is the way I treat my television, the way you'd choose a particular piece of music to play.

"I think if parents brought up their children to be selective about television, possibly television might take a quantum leap forward -- who knows? Instead of which, they use television as the soporific for the child. They shove the child in front of the television and know it'll keep them quiet."

One program that was no soporific was the fascinating 11th-season opener of PBS' "Mystery!," the four-part "Mother Love," starring Rigg herself. Her performance, as an obsessive mother who goes mad with jealousy and hate, won raves both here and in England, where she was awarded the BAFTA, the British equivalent of a combined Emmy and Oscar.

In "Mother Love," she said, she wanted to add an imperious note, a sort of tension to Helena Vesey, a woman Rigg described as having her "lid on too tight."

Producer Ken Riddington told a reporter that when he read Domini Taylor's novel, he wanted Rigg for the role. But Rigg said that Andrew Davies, who did the adaptation, had pictured "a sort of quiet little Englishwoman playing this part," she said.

"He was astonished -- and, thank goodness, not cross -- with the way that I did it. Actually, without even thinking about it, she became this other person."

Rigg said she read Taylor's book and was pleased that Davies "developed certain areas that weren't developed in the book -- for example, {Helen's son} Kit's father's life and that robust, warm, loving family. I think that was very clever because it was a counterpoint to the sterility of Helena's house. I suppose that was crucial."

The formidable Rigg also knows what she wants out of a production. In this case, she wanted to light up Helena's eyes.

"I had a little tussle with BBC Lighting over the closeups," said Rigg. "Nowadays they tend to do a sort of blanket lighting, very much bounced-off-the-ceiling lighting from above. I got on extremely well with the cameraman, but I did finally get what I wanted, which was lights in the eyes.

"The first two episodes, I said, 'Do what you want, but certainly episodes three and four, puh-LEASE give me SOME-thing to light my eyes, because that is the only way you can read what is going on in the mind.' And I won my battle."

It isn't difficult picturing the strong-willed Diana Rigg winning her battles. A veteran of the Royal Shakespeare Company since she was 20, she can intimidate with the inflection and delivery she developed there.

Yorkshire-born Rigg entered the theater over the disapproval of her parents, who had sent her from India, where she had lived since infancy, to boarding school in England at age 7. She recalls her childhood as happy -- her father was overseeing the building of the state railway at Jodhpur -- but after her mother returned to India, Rigg did not see her for 18 months.

"Bizarre," she says now. "It's a long time in a child's life, at 7. I loved her very much, but she was quite a stranger to me when she returned. My father was even more of a stranger because I didn't see him for two years. I think it probably did leave its mark."

So, like many a lonely child, she turned to the world of imagination. At 11, she portrayed Goldilocks in a school play; when she was 14, Emily Bronte. At 17, over parental objections, she enrolled at the Royal Academy of Dramatic Arts and in 1959 was admitted to the Royal Shakespeare Company.

But it was her 30 months playing Emma Peel in "The Avengers" (March 1966 to September 1969 on ABC, still showing on Arts & Entertainment and WFTY) that brought her international attention. The role lead to "Diana," an NBC series she later called "dreadful," and appearances in several dramatic specials on CBS. She also played the only woman James Bond ever married, a Spanish contessa, in the 1969 film "On Her Majesty's Secret Service," starring George Lazenby as Bond.

Three years after her divorce from Israeli artist Menachen Gueffen, in 1974, she gave birth to a daughter by Archie Sterling, whom she married in Manhattan in March 1982. (They are now separated.)

It was Rachel for whom she made what she called "a bit of a bargain," to curtail her acting career.

"It's how you view motherhood and how important it is in relationship to your career," she said. "I consider it rather more important than my career."

"If I was in a play which ran for six or nine months at the West End, then at the end of that I would not work for a while, so that she could see the end and know that I would be with her all the time after. She understands. I try and keep the holidays free, Christmas holidays and Easter.

"But I've never gone, since she was born, from one thing to another to another. Never, as a matter of policy. When your child was 19, 20, I would regret not having done it the way I could. At least my input has been as great as I could under the circumstances."

Like her mother, Rachel has appeared in plays at her boarding school, but Rigg said she does not encourage her daughter to follow her footsteps, largely because she regrets not having continued her own formal education.

"Once you enter acting, it tends to be very single-minded. And I think between 13 and 15 at school, you're given a great number of opportunities to learn about a great number of things and you tend to discount them if you only want in the end to be one thing when you leave school.

"She used to be interested in the theater when she was 7 and I think she's outgrown it, thank goodness. I don't encourage her at all. I don't approve.

"If she wants to be an actress when she's been to university, got her degree, fine. Then she may decide. By telling her she's got to go to university, I'm not restricting, but possibly equipping her, if she enters the theater, better."

Unlike Helena Vesey in "Mother Love," a woman who, Rigg said, "saw her son as an extension of herself, I see Rachel as completely separate, and I love the difference. That's the bit that I encourage, much more than being like me.

"And I'm not too possessive about her at all. I never read her mail or diaries or go into her drawers. My mother used to do that. I loved my mother a very great deal, but her curiosity about her children was somehow quite shameful. And this is what some mothers do. They can't stand their children having a secret life, which is what children have, and must have.

"If you have in fact brought them up with certain standards and beliefs, then only if they're lost emotionally do they lose that, do they not adhere to them. My belief in the way I've brought Rachel up is very strong. I may well be confounded."

Rigg seems fascinated by differences between the way her parents saw their role, and hers, and the way she is rearing her own child.

"I was not viewed as an individual until I was 16, 17, 18," she said. "I was brought up when children were to be seen and not heard. I was brought up to respect my elders, never question their decisions, ever, because they were elder, not because they were wiser. This gave me a very secure background, but it wasn't necessarily right."

Rigg said that Rachel once blamed a poor grade she had earned in geography on an inadequate teacher.

"If I had said to my mother I didn't like the teacher, my mother would have said, 'Rubbish. What are you talking about? Just do better. Don't question the teacher.'"

But after Rachel changed teachers, she came home with top grades in the subject. "Thus proving her correct," pointed out Rigg.

"We've changed and it's very good that we have. I think it's right that we do listen to our children."

"Rachel is heavenly," said Rachel's mother, "absolutely adorable. I keep on saying to her, 'When is it going to happen? When are you going to hate me and find me boring and dull? Just let me know. Please. In advance.'"

This spring, balancing her career with her bargain with her daughter, she'll star in Dryden's "All for Love" in London, fitting in her twice-a-year tapings in Boston for the "Mystery!" introductions.

She'll turn up again in March for an hour-long television celebration marking the 20th season of "Masterpiece Theatre," having starred as Lady Dedlock in its "Bleak House" several years back.

And from time to time, she'll do some writing.

"I write odd pieces for newspapers. I review books and that sort of thing. I don't think I'm terribly good at it. I think of all the arts, I admire the art of writing more than anything. I'd like to be good, to write well, but I don't."

In 1983, Doubleday published "No Stone Unturned," Rigg's humorous collection of disparaging theater notices.

She also would like to direct.

"But I've got to go to school. One of these days possibly I'll go to the BBC and do one of their courses. I think it's such a responsibility, directing. So much is entrusted to you that you must know everything there is to know."

If she ever does direct, she said with a laugh, "I'd be jolly kind to the actors."