She is, some say, the woman who dashed the hopes of dozens of lonely Washington matrons.

"Oh, dear," the former Jennifer Dyke McGougan, 48, cries at such a thought. "I hope they aren't sticking pins in an effigy."

If they are, it would be because until he brought her back from England after marrying her there this summer, Sir Antony Acland, 57, a widower and Britain's ambassador to the United States, was one of Embassy Row's most sought-after men.

But perhaps it was kismet. The marriage, it turns out, reunited the Dykes and the Aclands, who'd been joined in the 18th century, but separated three generations ago over some now forgotten tiffs.

It all started in 1746, when Miss Elizabeth Dyke, an heiress who brought the Devon-based Aclands considerable wealth, imposed as a condition of her marriage that the family name become Dyke-Acland. And so it went for a couple of centuries until Antony Acland's great-grandfather got mad and dropped the Dyke, and Jennie Dyke's grandfather got mad and dropped the Acland.

"Whether I can get Antony to add the Dyke again I don't know," says the new Lady Acland. "I doubt it."

She is a petite brunet with twinkling eyes that hint at a puckish nature in more relaxed circumstances. This morning, though, flustered at having her picture taken, she settles onto a settee in a drawing room at the embassy residence. It's an imposing room that British interior designer David Mlinaric made less so with blue-and-white print upholstery. Lady Acland and other embassy newcomers like to think it was done just in time for the 1985 visit by "the Waleses," as Prince Charles and Princess Diana are unceremoniously called around here, but the ambassador's social secretary says the redecoration was a couple of seasons earlier.

In an hour or so Lady Acland is expected at a potluck get-acquainted luncheon with the British Embassy Wives Association. And in the afternoon her diplomatic obligations will take her to tea with the wife of the dean of the diplomatic corps, Sweden's Countess Ulla Wachtmeister.

The purposeful commotion going on where tables are being set up across the hall is a tip-off that Lady Acland's day won't end at the Swedish Embassy. This night the Aclands will host a dinner honoring Hong Kong's governor, Sir David Wilson, a house guest.

"This is a large house with a lot of people going through it all the time," says Lady Acland, the daughter of a British army officer, who says she led quite a demanding and peripatetic life before she ever came to Washington.

She was a child in India, where the family, members of the British Raj, was "stuck" during World War II while her father went off to war. "The very first nursery rhyme I learned was Humpty Dumpty in Hindustani," she says. Afterward, there were postings in West Germany, where she later returned to study German literature. Traveling often from Heidelberg to Bonn, where her godfather was military attache', she saw "a bit of diplomatic life on a different level."

This level, though, is something new.

"I love people -- I really do," she enthuses. "It's fascinating meeting all the people who come through -- I would never have met {Sir David} if I hadn't been here. He's absolutely charming."

Still -- and here the stiff upper lip seems to quiver ever so slightly -- "It is tiring having people here all the time and having very little time to ourselves."

Married in late July, she hardly unpacked her bags before Acland's diplomatic duties intervened. When she hasn't been traveling with him on business, she's been up to her neck in the Washington social season.

"It's fun, and it's fun to do it together," she says, marveling at how her husband ever managed alone last year, though quick to add that he did it "beautifully."

"I'm terribly pleased that I am here to take some of it off his shoulders," she says.

Before she came, Sir Antony ran the residence, beginning his days by consulting with the embassy's three chefs on the following day's menus. Only later would he leave for his office. He still chooses the wines but she now meets regularly with the chefs.

"It doesn't sound like very much but I think it is something to take off his shoulders," she says.

At another embassy dinner -- this one for British Defense Secretary George Younger, with outgoing U.S. Defense Secretary Caspar Weinberger and his successor, Frank Carlucci, in attendance -- Acland is asked if he gave Lady Acland any pointers about taking over the house and running it. He says he only urged her to "just be herself."

"I had every confidence she'd do without any advice," he says, as the two pose for a picture.

"That's very nice," she says.

"I think I'm very lucky to have the staff. I couldn't do it without them," she says. "What is lovely is when we have a crisis, everybody sort of rallies."

"Things have to be done at very great speed. Last night 10 tables of 10 were in here," he says, referring to the ballroom, "and eight of 10 in there {the dining room}. All the dining room furniture had to be taken out, and all of this furniture, and then it all had to be brought back for the guests today ..."

"And suddenly there was a misunderstanding," she says, "and no flowers. So the wonderful thing was we had these lovely roses in the garden, and we all rushed out in the garden, and -- you see all the roses."

She's also helping outside the residence, enlarging Acland's circle of acquaintances by introducing him to people she is getting to know on her own, many of them wives of legislators and Cabinet officers.

"I think that's useful to Antony and nice for me," she says, since not all guests at an embassy party need be what she calls "pertinent" to a particular guest of honor. "We are both very interested in politics and so it's a good combination of our lives."

What must be pertinent is the reason the Aclands entertain in the first place. British government-related functions are one thing, but there are also endless requests for Britain's ambassador to host community or charity events, and that's a tightrope act Lady Acland is only beginning to learn.

"It's a difficult balance," she says of why one community group or charity event is selected over another. In most cases, though, the bottom line is whether there's a British connection.

"It's nice to do things that are British and American," Lady Acland says. "If we were asked to do something totally unrelated I think we'd probably say no. After all, this is part of Britain."

She had a preview of what she would be getting into when she paid Acland a visit that coincided with BBC television's big 50th-anniversary party last November. She was struck then by how many people came through the residence and how adroitly Acland handled it all.

By then, a 42-year friendship begun in childhood had turned into a long-distance courtship that had started the previous summer. He was in London preparing to come to Washington after winding up nearly 4 1/2 years in the Foreign Office as deputy undersecretary and later permanent undersecretary of state and head of the diplomatic service. A divorce'e, she was in London as one of three citizen judges presiding over two lengthy lower court cases.

They saw a lot of each other, and when it came time for him to leave for Washington she remembers that it was "awful saying goodbye."

She was a good friend of his first wife, the late Anne Verdon Acland, and had seen a lot of her when she was ill, the last time three days before her death in October 1984.

"She was a wonderful, brave person whom I had great admiration for. I saw Antony a bit after she died, and that Christmas he and Katherine came to my home in Devon because his parents lived not very far away. And I suppose we always kept in touch," she says.

In fact, the ambassador's 22-year-old daughter Katherine, who's in her fourth year of medicine at Bristol University, is the goddaughter of Jenny Acland's sister, who lived with Antony and Anne Acland in New York when the child was born.

"It's sort of a nice intermeshing of families," Lady Acland says.

Acland has two other children, Simon, 30, a banker, and Nicholas, 28, in corporate finance. Lady Acland has four: Emma, 25, a political secretary to Prime Minister Margaret Thatcher; Susanna, 24, married to a New Zealand farmer; Fiona, 21, in school in Washington; and Angus, 16, at Eton.

Divorced long ago, she says she has worked part time as a magistrate for nearly 18 years, and for six before that as a liaison between the London school system and inner-city children, many of them Asian and West Indian.

"I used to spend quite a lot of time going to visit them in their homes, finding out their problems, putting them in the right direction," she says. "A lot of them found themselves in court for one reason or another and it was really because of that I got caught up with the juvenile courts, and how I got recommended to be a magistrate."

She found sitting in judgment "a good intellectual exercise"; though she never would say she "enjoyed" it, she did enjoy using her mind "to work out the best solution for the person involved."

"I must admit I loved that," she says.

While women in Britain often serve as magistrates, Lady Acland says she thinks that has nothing to do with the feminist movement but with the fact that a lot of women have more time to give there. One of the surprises in Washington was discovering how many wives hold important, paying jobs.

She says that someday she may go back to being a magistrate. "I hope I'm on ice, because they very kindly said when I come back they'll have me back on the bench."

Meanwhile, she's working at the job of being Lady Acland. In one recent week, for instance, the Aclands hosted a reception for the African Flying Doctor Service and dinners for the governor-general of Hong Kong, for American and British naval personnel commemorating Trafalgar Day and for the former governor of the Bank of England.

"It's hard work," she says.