They were all there, clustered closely together on the second floor of London's National Theater. There was Tom Stoppard, looking like a very long and languid Mick Jagger, and Sir John Gielgud, fastidiously squinting over a neat beard, and Peter Ustinov, and Charlton Heston, and Beatrice Lillie, and Cole Porter, and even Franz Kafka, with his Mickey Mouse ears and black eyebrows and big luminous eyes.

Some were dead and all were two-dimensional, and yet, as a passer-by remarked, they still managed to look three-dimensional and exuberantly alive. They were part of an exhibition of Al Hirschfeld's caricatures, the first that the venerable cartoonist has had in Britain. Seven dozen of his works, dating from the 1920's to the 80's, have been loaned to the National by the Margo Feiden Galleries in New York, and will be on display outside its Lytteton Theater until Aug. 3.

Mr. Hirschfeld himself was at the exhibition's official opening tonight, and didn't lack admirers in and out of the theatrical profession.

Actress Buys Drawing

Michael Frayn, author of "Noises Off," rhapsodized over the cartoonist's ability to "be very mannered, very stylish, yet capture the essence of the character." Ron Moody, seen on Broadway as Fagan in the recent revival of "Oliver," congratulated him on "your marvelous rhythm, your strong lines, the way you get to the core of an actor and a role." Julie Covington, who played T.S. Eliot's doomed wife in "Tom and Viv" at the Public Theater last season, went one better. So struck was she by Mr. Hirschfeld's drawing of her that she bought it on the spot.

"I'm a bit longer here," she said, ruefully pointing to her nose as she contemplated Mr. Hirschfeld's portrait of Viv Eliot, with its black dress, black hat, black veil and stark black eyes, "but he's got her arrogance, he's got her nose-in-the air manner, he's got her class, which is upper-middle, he's got so much. I'm really terribly flattered to see it."

All around, the decades unrolled in caricature. There was Dame Judith Anderson as an improbable-looking Hamlet, and a swarthy Henry Fonda in "The Grapes of Wrath," and Grace Kelly and Bing Crosby in "The Country Girl," and Paul Scofield as a spectactularly hairy King Lear, and Anthony Quinn as the eternal Zorba.

"I try to capture what the playwright and actor intended the character to be," Mr. Hirschfeld explained to a passing British journalist. "I think the part is the thing, more than the personality of the performer."

But weren't some faces more difficult than others? Not exactly. "What's ulcer-producing, what takes times," he said, "is getting drawing down to the very simple. The ones full of pattern and needlepoint are easier. It's eliminating that is the trouble."

A drawing that particularly satisfied him was the one he did for The New York Times recently. Think of a cross between a bass cleff with feet and an exclamation mark with a clown face, and - no, you still haven't quite imagined the audacious astringency of Mr. Hirschfeld's drawing of Rene Auberjonois in "Big River."

Several British cartoonists attended the opening and joined in the chorus of praise.

"He has great powers of observation, he picks out individual quirks, down to the timbre of the eyes, " said Bill Hewison, whose theatrical caricatures for Punch are almost as well known in England as Mr. Hirschfeld's are in America. "Yet he can also reduce people to symbols, geometric shapes, and it works. There's a hairline between catching the quality of someone and getting it wrong. He almost always seems to get it right."

Mel Calman, who contributes cartoons to The Times of London, agreed. "He gives you interesting and exciting designs," Mr. Calman said. "And there's a lot of warmth and affection in his drawings too, not the awful biles and hostility you get so often nowadays."

John Jensen, another of Punch's regular caricaturists, added: "Yes, he can home in on a likeness and get it in a few lines. And he's been doing it consistently for years and years. He's the grand old man of our profession."