Long before Hal Holbrook donned his first Mark Twain mustache, and before James Whitmore began fooling with Will Rogers, folksy twang, and before Alec McCowen's discovery that people would actually pay to hear the Bible, Emlyn Williams was a one-man show.

"I got the idea from Charles Dickens in 1951," Williams said last week in a borrowed -- and stultifyingly small and dark -- apartment in New York where the Welsh actor/author/playwright had paused on his way here for "Dylan Thomas Growing Up," which opened last night at the Kennedy Center.

"I was reading his autobiography, and I suddenly thought: I'll dress up as Dickens and do what he did -- tell a story from one of his books." So after trying the act out on a few friends, Williams took it on tour, first across England and later America.

He arrived the year that Dylan Thomas died. And like Thomas, Emlyn Williams had escaped from Wales and obscurity through the good offices of the English language.

He may not have come to a comparably bad or early end -- Thomas died at 39 and Williams is 73 and going strong -- but Williams' story could certainly sustain an evening in the theater. In fact, it has.

In "The Corn is Green," Williams' sixth play and his second solid success (after the moody "Night Must Fall"), a young man marked for a career in the coal mines wound up, under a spinsterish teacher's guidance, winning a fellowship to Oxford.

Although the play is autobiographical, the coal mining was an act of dramatic license: In real life, Williams' father was a greengrocer, and the son -- who grew up in Glanrafon, Wales -- never worked a day in a mine. But the unpromising small-town surroundings, the dedicated teacher and the Oxford scholarship (plus subsequent and more unlikely adventures) were all perfectly real.

Miss Sarah Cooke -- the model for the teacher played by Ethel Barrymore on the Broadway stage and Bette Davis in the movie -- "could smell ambition," Williams recalls.('and in "George," the first of his two remarkable memorirs, he describes her as "the rarest at anomalies, a full-blooded spinster.")

But she was not full-blooded enough, at least initially, to see the wisdom of Williams' decision at age 18 to enter the theater, or to be kept abreast of certain touchy details in his private life.

The second volume of Williams' memoirs, called "Emlyn," tells of his early years in the London theater, from 1927 to 1935, interspersed with a chronicle of two homosexual love affairs followed by an eventual happy marriage. There is a fairly matter-of-fact account, too, of a transitional period when he was paying his male ex-lover to teach his wife-to-be how to drive a car, and the three of them were living together on the same London premises.

Marriage and the 1935 success of "Night Must Fall," with Williams himself as a brooding murderer, were the events that brought order to a confused life. (They are also the events that close out the two volumes and 850 pages and autobiography he has completed to date.)

Williams never met Dylan Thomas, who was expected but failed to appear at a performance of the Dickens, show one night in Los Angeles in 1953.

"The irony of it is that if he'd lived, he almost certainly would have gone into the theater," says Williams, citing the success of Thomas' radio play "Under Milk Wood."

Williams added Thomas to his repertory after reading several Thomas stories at a benefit for his widow and children, and liking what he had read.

Williams has now done the Thomas show about 800 times, he estimates, and the Dickens about 2,000 -- or the equivalent of a five-year run (but in tolerable installments of several months each. "If I did it five years running, I'd feel a little jaded," says Williams).

he concept of the one-man show had a shaky start, especially on this side of the Atlantic, where many of the theaters were a lot larger than the audiences during Williams' first 1953 tour. "They didn't have those marvelous college theaters then, or if they had them I didn't know about it."

But 25 years later, Williams has decided he prefers performing by himself. He finds it "less exhausting" -- even though his current American tour will take him to some 25 cities in 20 states.

He uses no props and no scenery, and says the secret to holding an audience's attention is not to have "one superfluous word."

"I call it a 'solo entertainment,'" says Williams. "A 'reading' is a dreary word. I try to avoid it. It's story-telling, really. It's back to the Arab marketplace."

Williams has made recent appearances in a TV version of "David Copperfield" with Laurence Olivier and Ralph Richardson, the Rolf Hochhuth play "The Deputy," and Robert Bolt's "A Man for All Seasons" (succeeding Paul Scofield as Sir Thomas More).

"If a marvelous part suddenly came along . . . " he says, but has trouble finishing the thought since, he explains, he has been booking himself so far ahead it would be hard to take any part, however marvelous.

In 1974, Williams collaborated on the book and lyrics to a musical of "The Corn Is Green," reset in the American South and starring Bette Davis. It would have been a first for both author and star, but Davis developed back trouble and the show had to be abandoned in Philadelphia.

"It was disappointing of course," says Williams, adding that director Joshua Logan still talks of reviving the venture. "But you've got to have a big star for the part."

Despite his bookings, Williams' schedule still leaves him with a fair amount of free time, which he has just utilized to write a novel -- his first in 60 years, he says.

His last novel, a historical romance entitled "Hearts of Youth," was composed at the age of 12. "So I trust I've matured," he says.