Britain's Stephanie Beacham has got a jolly good career going on this side of the Atlantic.

It's Jeff and Fallon's wedding day on the set of The Colbys. John Forsythe looks the part of proud papa while John James and Jack Coleman impatiently jostle each other. Charlton Heston strides around looking decidedly grumpy. Ricardo Montalban and Diahann Carroll match their actions on take after take, and Emma Samms, as Fallon, looks extremely pretty in pink. The altar is framed with men in charcoal gray morning suits and a florist's shop of fresh flowers.

Amidst all the familiar faces sits a woman who, although she isn't nearly as well known, commands equal attention by doing literally nothing. That is a quality called presence. English actress Stephanie Beacham has it in spades.

An attractive red-head with a wasp-size waist who looks years younger than she probably is, Beacham has combined theatrical performing in London with a haughty sense of sardonic bitchery to create the show's most memorable character, Sable Colby. If Joan Collins is the rock on which Dynasty is built, Beacham, in her own way and on her own terms, is creating the same sort of base in The Colbys. In a show that lumps together big-name veterans and inexperienced pups, she is, in this country, an anomaly, an accomplished newcomer - to American television and to soap stardom.

During a break in filming, Beacham played hostess in her on-set trailer and, although dog-tired from a nerve-wracking schedule, related the curious turn of events that brought her from London to The Colbys.

"Esther Shapiro has a friend named Marian Rosenberg. Now, Marian, who is both a producer and an agent, had made a film several years back called Tam Lin, in which I had starred with Ava Gardner. Esther had trouble finding the right actress for Sable and, in describing her, suddenly Marian thought, 'If Stephanie Beacham has grown up as I think she'd have grown up, she'd be perfect for this part.' The very day they had this conversation, my London agent flew in to meet with Marian to set up a reciprocal talent arrangement and the first picture he put on her desk was mine. Marian turned over the picture to see my name, said 'Oh my God' and called Esther Shapiro saying, 'I've found your Sable.'"

If coming to the attention of The Colbys producers was somewhat unusual, Beacham readily admits that the audition took her even more by surprise. "I had just finished the run of a very popular television series, and I was exhausted. I was off on holiday and told my agents, that 'No, I would not audition.' My feeling was that they were coming to London to do what they usually do, which is to prove that the choice they've already made in Hollywood is the correct one." (Indeed, numerous sources have indicated that Faye Dunaway was the first choice for Sable, but negotiations broke down when she failed to waver on what was considered an exceptionally high fee.)

Then fate stepped in. A London neighbor, who had promised to feed Beacham's fish, called to say that she couldn't feed them because she'd lost the house key. Rushing back to town to save the fish, Stephanie agreed to her agent's request and proceeded to the audition.

"I still didn't think much of it," Beacham remembers. "I wasn't silly, of course. I brushed my hair and cleaned my teeth. You don't want any film on you to go into a country where one day you may want to work, so you must look your best. But when I got to the place and walked in I thought, 'I know this smell.' There was the smell of hideous trembling in that audition. All of these frightfully well-known English actresses pulling far too many frocks around on hangers. I suddenly realized that this was being taken very seriously. Many of these actresses had brought their own actors to read the scene with; they'd been rehearsing. Thankfully, I have a photographic memory, so after a quick look at the script, I read. The only thing that came to me instinctively was that I should look up at the actor playing opposite me and that whatever he said I should talk back sense." She pauses for effect, takes a sip of juice and gestures lightly. "That, as they say, is history."

Beacham's history is unknown to most American viewers and for the good reason that The Colbys is her first experience in American television. The bulk of her work has been in the English theater, on occasion with her husband, actor John McEnery. Shakespeare and Chekhov aside, their happiest collaborations have been their daughters, Phoebe, eleven, and Chloe, nine. In fact, whatever disorientation Beacham may exhibit due to her crushing schedule evaporates as she speaks with great affection and yearning for her children who are, at present, at school in London.

"Every Tuesday, I post the children something and we speak every Saturday, so there is a structure. In fact, I just sent them some colored tissues because they've both got stinking colds. It's so ridiculous, ten dollars on postage and two dollars worth of tissues. Phoebe is gorgeous and Chloe is pony-mad. She got a Cabbage Patch horse for her birthday, she's all into galloping, bolting and cantering at the moment. That's natural for little girls; their feet turn out for ballet and then in for riding and then out again for ballet and then it's boys.

"Phoebe's gone straight into boys. No, not quite. She still tells me that the idea of developing breasts is the most disgusting thing that's ever going to happen to a person.

"When she was very little, Phoebe was in a pre-school and all the children were gathered on a mat and asked to tell what their fathers did for a living. One child would say, my father's a fireman, and the other, my father's a doctor and so on. At the time, John was appearing in repertory with the Royal Shakespeare Company and when the teacher finally got to Phoebe she said, 'Well, I think it's Twelfth Night tonight or it could be Othello!'"

While acknowledging that she may have two budding actresses on her hands, Stephanie insists that "the girls know it's incredibly hard work" and offers that acting was not her first chosen profession. "I'm quite deaf, you see and early in life I thought I would like to teach music to deaf children, because while they can't hear as we do, they can feel the vibrations of the music." It should be noted that Stephanie wears no visible hearing aid and appears to get along relatively well, but it is a handicap she has no compunction discussing as well as being a topic that is still something of a cause with her. Recently she appeared with several other Colbys stars at a fund-raiser for The Starlight Foundation, a non-profit organization that makes the dreams of dying children a reality.

"Years ago, I wouldn't have appeared at a benefit like that. I simply would have sent in an anonymous donation and let it go. Thank goodness, I've grown up enough to know what show business means; it's not just the acting, it's everything else as well, and I'm terribly keen on lending my name to these social functions. Of course, when you're playing someone as vile as Sable, it's not such a bad idea to let yourself be seen in public as you are - an ordinary, jolly, though sometimes curt-of-tongue, woman. I'm really a jolly human being! But Sable... poor old girl, she's got tunnel vision and this thing about her son and this dreadful life and I feel very sorry for her. I was thinking the other day, could I be friends with Sable? Yes, I suppose I could cope with her, but I don't think Sable would give me another look. She wouldn't even notice me. She needs a friend like me, but I don't think she'd have the sense to seek me out."

Beacham has high praise for her television cousin, Joan Collins. "Joan Collins has it!" exclaims Stephanie. "What I've done about the comparisons I knew would be made is absolutely zilch. I couldn't imitate anybody, there's no point. And I'll tell you quite honestly that when I first came to town I thought very little of Joan Collins. I don't think I took her seriously. Now I take her extremely seriously and I admire her enormously. To do what she's done on Dynasty and then to have the energy to do her own projects, well, she has my full respect."

As for her own future projects, Stephanie Beacham is still feeling her way. "At the moment, all I want is to finish the season so I can be with my family. I've been in a hotel for so long, I need a solid home under my feet. but I'm pleased with the response to The Colbys. We're going to be back next season and, yes, there has been interest from other quarters." She subtly knocks on wood (or in this case, formica). "It looks as if I want a career in America, I'll jolly well have one!"