Some were sages, others were fools, but all were daring, ambitious and romantic. Social climbers, soldiers, painters, wits, inventors, businessmen and beauties, they fled a world they knew too well for one that they invented.

"Return to Albion: Americans in England 1760-1940," which opens today at the National Portrait Gallery, is a show about their dream.

But the Yank expatriates dreamed of Albion, not England.

Albion was different. Albion, a romantic designation for ancient Britain, had castles, "sweet women, dry champagne," marquises and strawberries and all the Old World's graces.

Americans, wrote Henry James, were "vulgar, vulgar, vulgar." In a famous, foolish passage he enumerated their flaws:

"No sovereign, no court, no personal loyalty, no country gentlemen, no places, no castles, nor manors, nor old country houses, no Oxford, nor Eton, nor Harrow, no sporting class-no Epsom nor Ascot."

Filled with manuscripts and paintings, rifles and recordings, photographs and snuffboxes, this delicious exhibition, which runs through Sept. 20, is less art show than parade.

It begins with Benjamin West, the painter, who was born in Springfield, Pa., and arrived in England in 1763, and ends with T.s Elliot of London and Missouri. Here, stumbling or prancing, come with Jimmy Whistler, Robert "Steamboat" Fulton, silly Nancy Astor, sneaky Gilbert Stuart, acerbic Ezra Pound, and Samuel F.b. Morse. There, marching beside them, are the illustrious prognitors, Winston Churchill's mother, J.p. Morgan's father. Here, too, are the works these expatriates created-"The Golden Bowl," "The Waste Land," "Home Sweet Home," the submarine, and those they bought and sold-peerages, department stores, palaces and showgirls.

Whether hungering for culture, husbands or adventure, the driven young Americans fled to Albion for love.

The men, not all, but many-Washington Alston, Washington Irving, Jonathan Sturges, Samuel Morse and James-were of pallid masculinity. In brawny, raw America, bachelors were suspect, esthetes were thought prissy, while at Oxford or at Eton, in Park Lane or the Cotswolds, if delicate young man pledged themselves to beauty, or to one another, no one seemed to care.

The Britons of the better sort did not blanch at eccentricity. Ezra Pound affected a single turquoise earring, trousers of green billiard cloth, vast cloaks and black sombreros. Whistler wore a monocle.

Very wealthy, very odd William Waldorf Astor, the first American to spend his way into the House of Lords, and whose portrait we see here, has his London office paved with "marble, jasper, porphyry, and onyx." In addition to his peerage, he purchased phony pedigrees,and Clivedon House and Hever Castle.He then rented Lanesdowne House in Berkeley Square where, among its 25 ballrooms, Astor-"Waldorf by name and walled-off by nature"-splendidly resided in a "solitary state."

His just-as-dotty daughter-in-law, the Viscountess Astor (born Nancy Langhorne in Virginia), was the first elected to the House of Commons. There she warned the world against the Communists, the Jews, hatd liquor and the Catholics (the latter, she once warned the House, were infiltrating the BBC). Winston Churchill called her the "American virago." "Winston," she told him, "if I was married to you I'd put poison in your coffee." To which he replied, Nancy, if I was married to you, I'd drink it."

And there is Harry Gordon Selfridge, inventor of the "sale," and founder of the grand department store on Oxford Street who spent his cash on showgirls. Whistler had remarked, "Certainly the Englishwoman succeeds, as no other can, in obliging men to forget her sex." Apparently Selfridge agreed. It is said he spent 2 million pre-war pounds buying jewels, houses, furs and cars for his nubile favourites, French chanteuse Gaby Deslys and the Dolly Sisters, twins from New York. In the last years of his life, Selfridge, old and bankrupt, was often seen in London queuing for the bus.

Painters from the New World, whose works are on view, were among the first expatriates to set sail for the Old. Benjamin West had prospered there, becoming the second president of the Royal Academy and a close friend of the king's.One by one, his countrymen-Copley, Stuart, Trumbull, Allstor, Benbridge, Sully Fulton, Morse, the Peales and many more-set out to seek his guidance and follow his example.

The heiress came later. Jennie Jerome, daughter of the "King of Wall Street," was among the first and the most illustrious. She married Lord Randolph Churchill in 1874. An editor, writer, a gifted politician, and Winston Churchill's mother, too, she was hailed by the British press as "the most influential Anglo-saxon woman in the world."

Mary Leiter, whose father, Levi, was one of Marchall Field's partners, married just as well. Lord George Curzon, whom she wed, was so unusually eligible that he was dogged by doggerel:

My name is George Nathaniel Curzon I am a most superior personMy cheek is pink, my hair is sleek I dine at Blenheim once a week .

Their love affair was splendid, brief, romantic. He was named viceroy of India. She joined him and reigned briefly there, then fell ill and died. Lady Curzon was mourned as a sort of flawless princess. Maud Burke, who changed her anme to Emerald when she became Lady Cunard, was recalled for her malicious wit. Once, when she caught Somerset Maugham departing from a party, she insisted that he stay. "But I must preserve my youth," he said. "Then why didn't you bring him with you," she replied.

While many of these expatriates lived in awesome luxury, some were not so lucky. John Trumbull, whose father was a leader of the American rebellion, spent seven months in prison. Whistler went bankrupt. Gilbert Stuart survived many scrapes before he returned to his native land. "I believe the real cause of leaving England was his having become tired of the inside of some of our prisons," opined by Sit Thomas Lawrence. "Well, then, afterall," said Lord Holland, "it was his love of freedom that took him to America."

A number of these travelers finally returned to the New World, some of them in triumph, others in disgrace. Neerly half a century after he arrived in London, with three pounds in his pocket, Ezra Pound, the master editor, was returned to Washington and locked in St. Elizabeth's. Philanthropist George Peabody who gave a museum to Havard, $2 million to the southern states for post-Civil War education, and even more to London's "deserving poor," was, upon his death, given a splendid funeral in Westminster Abbey, an honor, it was noted, "coveted by nobles and not always granted kings." H.M.S. Monarch , the newest warship in the British navy, then brought his body home.

John Singer Sargent died in London, as did James and Eliot. The names of the latter two have since been engraved in Westminster Abbey, where their adpoted kingdom honors her most distinguished dead.

"Return to Albion" was organized for the gallery by Richard Kenin, an Oxford-educated American, who was accompanied his show not with the usual catalogue, but with a well-researched, well-written, and often charming book.

This is just the sort of exhibition the National Portrait Gallery was established to present. The gallery, after all, is less a gallery of art than a museum of history and people. The artifacts, portraits and manuscripts on view, Lady Curzon's peacock gown, Audubon's bird rifle, the Golden Bowl presented to Henry James at 70, are by themselves near mute. But accompanied by Kenin's words, and installed here, in context, they begin softly to sing the expatriate's odd, conflicted song.

Kenins's exhibition opens with two epigraphs. The first is a quote from Ralph Waldo Emerson: "Men run away to other countries because they are not good in their own, and run back to their own because they pass for nothing in the new places." The other if from James: "My choice is the Old World, my choice, my need, my life." CAPTION: Picture, Lady Jennie Churchill and sons Jack and Winston, above, and T.s. Elliot by Wyndham Lewis.