Emmanuel de Margerie is, as his father and grandfather were, an Ambassador of France, the highest rank in the French diplomatic service. His great-grandfather Henri Germain founded the Credit Lyonnais, one of the world's leading banks, and his great-uncle Edmund Rostand wrote "Cyrano de Bergerac." A connoisseur of art, he was director general of the museums of France, a position that has been held only once before by a diplomat, under Napoleon.

But such distinguished lineage and diplomatic agility are not the only reasons that Washington celebrated the return of the debonair ambassador and his elegant wife, Helene, in a way rarely seen in this city of frequent comings and goings.

"In Paris it seemed that was the perfect place and they belonged there. The same was true later of London. But then they are exactly right for here," says Washingtonian Deeda Blair. "They are the perfect French characters. Everyone is so pleased they are back." The Blairs were among those -- including Evangeline Bruce, Susan Mary Alsop, Maida and Jan Mladek, John and Evelyn Nef, Robert and Luisa Biddle Duemling and Pam and J. Carter Brown -- who scheduled dinners in the couple's honor the minute they arrived.

De Margerie credits the English governess he had as a child, who baptized him "Bobby," the name everyone uses, for his genuine sense of fun. "That marvelous person. She had a philosophy of life -- 'Life is fun,' " he says. "Even when she was at the end of her life and quite poor with problems of health, she used to repeat, 'Life is fun.' She has given me the taste of seeing everything that is interesting in life."

Former president Valery Giscard d'Estaing appointed Emmanuel de Margerie head of the museums of France in 1975, a job that has served him well as a diplomat. In visiting provincial museums, acting as adviser to the mayors of those cities, "I saw a full spectrum of political opinion in my country," he says, "and I also met people from other ways of life."

In fact, that is how he met Roland Dumas, the newly appointed French foreign minister. Dumas was the principal lawyer in settling Pablo Picasso's estate after the artist's death, "a considerable problem," says de Margerie, "because Picasso had a number of children from different ladies, with complicated family interests. There were all the ingredients for a very long litigation . . . a chance for a very juicy thing to go on for years and years and years . . .

"Instead of going in for litigation, Dumas went in for arranging everything between everyone. That is how I met him, and that is a quality which is good in the foreign minister."

As head of museums, de Margerie dealt with problems of security and budgets, including funds for the Centre Pompidou. "I knew it would put Paris on the map with creative, very contemporary art," he says, "and it was a difficult situation because a lot of money had been given to it, and the rest of the museums were rather poor relations and feeling a little miffed."

Before he left, the budget of the French museums had doubled and the government had approved, for the first time, a five-year plan for the development of museums. "That was essential for embarking on great projects," says de Margerie. It gave assurance, for instance, to the last few remaining firms in Lyon that could produce silks for the restoration of the Palace of Versailles; previously, they had never been sure about work even two years ahead. "They had the certainty it was worthwhile recruiting younger people to keep on the great tradition of French artisans."

But his crowning achievement, he says, was persuading the government to create the Musee d'Orsay, a former train station that will open next year as a center for 19th-century art. De Margerie is now head of the society of friends of that museum. "I've kept my old bonds with the art world," he says.

The museum job came with an apartment in the Louvre with views of the Seine and the Tuileries gardens. "Bobby had a small key which opened all the doors of the whole Louvre," says Helene. "Sometimes we would go at night with a flashlight by the little tiny staircase in the back of our flat, straight in the Gallerie Medici with the big Rubens. Sometimes we did for our pleasure, but more often with a great curator or collectors or donors, and we took them and it was always a great treat."

"I never got accustomed to the idea of living in the Louvre," says de Margerie. "When we used to go back at night from a dinner and realized that this huge pile of masonry was my home, I could hardly believe it. From one end to the other, the Louvre is as long as the whole Ile St. Louis."

They lived there just over three years. "I promised that when I was going to be called back to the fold I would not drag my feet," says de Margerie, "and I didn't." Besides, he was pleased about his next appointment, as ambassador to Madrid.

"That's one of the marvelous aspects of the diplomatic job," he says. "You can be interested in everything . . . You are constantly busy, shifting from one order of preoccupation to another one. The general curiosity of the mind can always be kept on its toes."

Two years ago de Margerie was appointed Ambassador of France, a title that puts him always at the administration's disposal. "I make no bones of the fact that I was really very happy with it," he says, "because my father was ambassadeur de france and my grandfather was ambassadeur de france."

The only place that all three served was Madrid, but de Margerie's grandfather was also in Washington as counselor during the term of President Theodore Roosevelt. "The president was a very military man, and my grandfather had been in the Hussars. The president told him, 'You must always come in your Hussar uniform,' " he laughs.

"At that time there were only 14 diplomatic missions, and Washington was a small town . . . very much a family life, and everyone used to be very close. And my grandmother, who was only 21 at the time, used to go out riding with a lady, Alice Longworth, who we knew when we were here 12 years ago when I was deputy chief of mission -- a very amusing old lady, a formidable wit."

The de Margeries have returned to Washington with a shaggy, frisky dog named Topsy, rescued from a shelter in London, and an impressive art collection, both comfortably in place in the ambassador's residence on Kalorama Road. Among the artworks is a bust by the 19th-century American sculptor Hiram Powers, who had such success with "The Greek Slave," now in the Corcoran Gallery, that he made several copies of the head. "It is amusing to bring it back to Washington," says de Margerie.

He bought his first work of art at 14 1/2, a Chinese painting he still owns. Is it a good one? "I have no regrets when I look at it," he answers with a grin. "I have always been as interested in eastern art as in western art, just as I am as interested in modern and contemporary art as I am in old art . . . It is embarrassing to say so, but I just happen to come out of a family where culture was a prime necessity for life."

Helene de Margerie's father was an art collector, and she remembers being taken by her parents to visit antique dealers. "It is incredible how much you learn at age 8 or 10," she says. "I probably have a sensibility for furniture as a result."

The de Margeries have two children, a daughter who follows her parents' devotion to art and a son who, with his wife, recently graduated from the elite Ecole Nationale d'Administration. He chose finance, she chose diplomacy.

Although de Margerie says he has given his wife "a full-time job," he admits feeling guilty for interrupting her career in microbiology. During one long stay in Paris she earned her doctorate, and while her husband was head of museums she returned to the lab. "But it's a science which goes so fast in genetics and engineering and all that," she says. "The second time it was difficult to catch up."

She nevertheless considers herself lucky, free to travel and share in her husband's work. While de Margerie was minister at the French embassy in Tokyo, she immersed herself in Japanese literature, and learned enough of the language to need no interpreter.

"It is one of the jobs where you can be a team," she says. "He is the important part of the team. I can just go along."

When President Francois Mitterrand asked de Margerie, who was minister here in 1971 and 1972, to return to Washington, he warned him that "Washington was going to be different." Indeed, while driving around the city before Christmas, de Margerie discovered what he calls, smiling, the "gentrification" of the city behind the Capitol.

"Gentrification is a term we learned in England," he says. "In London they have all these tiny charming little houses, in the 19th century lived in by laborers. Now, all of these young couples are going there and rehabilitating the houses also."

De Margerie excitedly lists the museums that have opened since he last lived here -- the Air and Space Museum, the Hirshhorn, the East Building of the National Gallery of Art -- but his tone changes as he speaks of another recent development. "One of the sad facts of the modern age has been the development of terrorism," he says. "We have been dealt a considerable blow in France recently when General Rene Audron a defense minister was murdered in Paris. Everyone has got to take great precautions."

Before their return, the de Margeries were urged by predecessors to get out and see the country, advice they'd heard before and heeded. Helene de Margerie remembers Oliver Hardy, then British ambassador to France, telling them just after they were married and leaving Paris for the first time, "Don't forget, if you really want to know my country, go and see all the industrial cities. Don't stay in lovely cities like Bath."

They discovered their own country in more than 15 summers traveling on mobylettes, stopping at little inns and occasionally a good hotel "if we had been without a room with a bath for a few days," she says. She tells the story of their arrival at one smart hotel, pushing their stalled bikes and looking very dusty. The doorman "with lots of gold on his jacket" escorted them to the back entrance. The woman at the front desk gave them a quizzical look. And when they showed their diplomatic passports, "I thought she was going to faint!" The next morning, as they were leaving, the doorman held her bike for her "like a fine horse," she adds gleefully.

In their wanderings, the couple found a special attraction to the southwest, particularly Gascony. One day they stumbled upon the ruins of Mazeres, the ancient residence of the archbishops of Auch, some parts of its mix of architecture dating back to the 12th century. It wasn't for sale at the time, but three years later it came on the market and they snapped it up.

De Margerie teases that they are now slaves to their restoration of this historic monument. "It had gone down, was completely derelict, everyone thought it was going to be finished forever," he says. "We tend to think that if people like us don't do it, then what will happen to places like this?"

He gives visitors to the embassy residence here an entrancing tour of the house, now full of their own and the government's art. In the front hall hangs a portrait of the Comte de Vergennes that de Margerie moved from the old chancery. "He was instrumental in your independence and a great friend of Dr. Franklin, and involved in the negotiations of the Treaty of Paris," he says, obviously enjoying the connection.

A large Meissen bird has been placed on a table under a Bonnard in the drawing room, the colors of the plumage picking up those of a tablecloth in the painting. The boiserie is where de Margerie has hung most of the modern art, including drawings by Aristide Maillol ("People are rediscovering him"), abstract painter Serge Poliakoff and draftsman Sam Szafran. But "we didn't bring our whole collection," he says. "Some things were left for the house in the country," in Gascony.

He has overseen the hanging of tapestries and modern paintings in the huge new marble chancery on Reservoir Road as well, and hopes that its auditorium and exhibition area will contribute to the cultural life of Washington. "It has cost the French government a handsome amount of money," he says, "but we think it is good for American relations."

Although many events will be held there, the most coveted invitations will be to the embassy residence, where Helene de Margerie works closely with chef Francis Layrle. She takes great care with the planning of menus, even down to the colors. "Sometimes I realize a dinner is completely pink, with tomato soup, then lobster, then strawberries," she explains. "I say, 'No, you can't have a pink dinner!' "

During one of the first business luncheons at the embassy, she sat in her office testing the meal simultaneously. "I've got to discover what Americans really don't like," she says. "I'm not sure about liver or brains -- that is for us a treat, except for Americans traveling a lot in France."

The de Margeries are already involved in the forthcoming centennial celebration of the Statue of Liberty, given by France to America. "The man who was the head of the committee 100 years ago in France was a M. de Laboulaye, the ancestor of Mr. Francois de Laboulaye former French ambassador to the United States , who is president of the committee for the celebration in France," he points out, delighting in one more tie between the countries.

The forthcoming anniversary of V-E Day will be far more complicated. "I think one has got to be careful about the way one approaches these great dates, which can create delicate problems," says de Margerie. "Last year we had the ceremonies in Normandy. As we did not want them to be an object of misunderstanding between ourselves and our German friends and allies, my president invited the German chancellor, Mr. Helmut Kohl, to come to France, and together they went on a pilgrimage to Verdun, where so many people had died during the war.

"And when they were at Verdun, as they were going up the hill my president extended his hand to Chancellor Kohl and they went up hand in hand, and that was a sort of symbol of what relationships between nations must now be. Delicate problems can sometimes be turned to good use."

Spoken like an ambassadeur exemplaire.