Ralph Steadman, the British cartoonist and illus- trator, has been in New York barely 36 hours, and already he's been making trouble. He has taken a self-portrait from the office of Rolling Stone publisher Jann Wenner--a portrait worth "a couple of grand" today though Wenner, years back, paid him $60--and hidden it. Aaah, when the publisher finds it missing, he should go mad, he happily says. He has gone to a smart party at the Cafe Central, and told a director what he thought of his short-lived film on Hunter Thompson, his sometime partner in combat journalism, his pal. And last night, he must tell someone, though how will he ever explain it to his wife, the incident with the hooker.

He can't stop talking about the hooker.

He is obsessed with the hooker.

She was on the street when he became fed up with all the smart people at the party, a freezing cold night, and she accosted him with a story to win the heart of a social critic--she needed to use a bathroom. It couldn't be the lobby, she'd be thrown out of the lobby, it had to be his room, she said. She stayed four hours, during which she looked over his latest book ("You did all of this, Ralphie? The pictures, too?"); they talked; she watched television; he dozed fitfully and fearfully; his system was in overload; curious, frightened, exhilarated. When she left he gave her all his money. A highly satisfying encounter, finally. She had gotten what she wanted. And so, as you will see, had Ralph Steadman.

A scratch, a blot, a slash on the page--that's the style. Social critic, illustrator, Steadman's been called the most savage political cartoonist of our age. Think of Guernica in pen and ink, its subject not war but everyday life: Las Vegas, a political convention, the Kentucky Derby. He works extensively for the British humor magazines and also done children's books, but he's best known in this country, where four years ago he was named Illustrator of the Year, for his work in Rolling Stone with Hunter Thompson--drawing so angry, so vicious, you want to turn your head away.

What brings him back to this country now is a solitary and gentler work, a playful and passionate book on Leonardo Da Vinci, "I Leonardo." It is more than a collection of illustrations on Leonardo's life, based upon three years of work and research; Steadman does not merely theorize about the man, but attempts to go inside the artist's bones.

Leonardo painted the Last Supper as a mural; Steadman painted the Last Supper on his guest bedroom wall. Leonardo built a flying machine; Steadman, working with an old tent in his garage, built one, too; he describes it as a beautiful Renaissance bat.

The book is Leonardo filtered through Steadman, written so you're never quite sure where one begins and the other leaves off. He did this on purpose--and purposely included inaccuracies--just to twit academics, whom he loathes.

He also changed facts, now and then, because he did had grown so fond of his subject. Leonardo, in fact, was never able to make his flying machine go. Steadman was able to make his own airship fly, and in his book, he lets Leonardo's machine fly, too.

"He never thought of the fixed wing, only of the moving wing, so he had too much machine," says Steadman. "If he'd thought of it, he'd have flown. I wanted him to fulfil his dreams," he says. "I didn't want him to be some poor bugger."

"What are you drinking?" That's the first thing he wants to know. He, the only fellow in the Berkshire Hotel bar in jeans and a down vest, is drinking vodka, straight, and a Budweiser chaser, strong brew in Manhattan for 1 in the afternoon. In his hotel room, he keeps drinking them. He's a stocky man, perhaps 5-10, graying, nearly pudgy, the warmest angry man you will ever meet. He answers everything, revealing both income ("Forty-two thousand pounds my last tax return, since I work like a bastard") and time on earth.

"Forty-seven years of age," he says, "and I feel every bit of it."

Even so, on the basic business of the interview, his attraction to Leonardo, the selling of the book, he is reluctant to speak. It is not uppermost on his mind. What is uppermost are his adventures with the lady of the night, the evening before. He talks about the lady of the night for a half-hour and more, returning to her over and over again; his sympathies for a person who find herself out on a freezing night with a full bladder ("I know what that's like"), his fear that she wanted more than a warm room with a toilet ("You're not having me on, are you? I'm just a simple Englishman"). He mimics the way she talked and poked about the room; he repeats, seemingly verbatim, her story of her child and her troubles and her life.

"I was curious, " he says. "But nothing happened. Nothing happened, because I didn't want it to happen, I didn't want to be implicated in that weird kind of thing; first of all, disease--I like good clean sex and I am happily married; but I am interested in the seamy side of life . . . She wanted shelter and I gave her shelter; she wasn't beautiful, but that's not the point--oh, yes, it is, if she had been beautiful I think I would have, you mustn't publish that . . ."

He speaks of the street life of America.

"I came here for the first time in 1970. I walked down the streets, I could not believe what I was looking at. I took a camera down Skid Row for hours on end being accosted by guys who said, 'Give us a dime, buddy.' I remember one--this is in my book on America--his face looked like a bomb site and he touched my arm and he said, 'Give us a dime, buddy, this is a hard town to get started in.' "

He roars with laughter; it is often the kindest souls who have the greatest capacity for rage.

"I had a pocketful of quarters, so as they came up I could give them a quarter and take everything down with a minimum of conversation; drunks coming towards me, drunks asleep on the sidewalk . . . I walked the sidewalks of New York looking for what it was I was looking for, and what I was looking for was the screaming life style of America; what is so wrong with this place and why do I react so horribly against it . . ."

There must be the same street life in England?

"No," he says firmly. "Here it's raw. And I'll tell you, it's the rawness that attracts me and frightens me. It frightens me, because I am susceptible to it. I am curious and I want to see what happens next. I couldn't leave that lady on the street. I wanted to know what was going to happen . . . I hate it and it fascinates me. I don't want to be part of it and it fascinates me. I try to shun it. And it fascinates me."

There's a glow liquor gives to a room on a cold winter day; it heightens conversation, anyway, that's certain, and here's Steadman, at times raging, at times playful; posing in the bathtub with a pencil up his nose or a shower curtain on his head, and speaking, at last, of how he came to spend three years of his life doing a book on Lenoardo.

"It was a remark of Sigmund Freud . . . He said that Leonardo was a man who woke up in the dark, he woke up when the whole dark world was still asleep; that's a pretty lonely feeling, I think, and that's how his whole life went. He kept on inventing things, doing things, that no one had a purpose for . . . it was like having a telephone number without a telephone.

"He wasn't a company man; he was simply a man who did what he wanted to do . . . And when he died, his work was simply dispersed and lost for 400 years. And when it came to light again, it had already been invented, it was terrible, everything had been done, even flying machines . . ."

He related to this?

"The loneliness, I think, the way you seem removed from the sort of general pattern of the way people want to live their lives," he says. "Sometimes in restaurants I hear people say, 'Why does he look like that, that slob?' . . . I hate the lot of them . . . you see so many of them in smart restaurants, like downstairs . . . faceless, pointless people inhabiting offices in New York, doing pointless jobs . . . and academics, I hate academics, they kill everything, they are death to curiosity . . ."

Oh, the rage of Steadman. You see it in his work, that furious explosion of slashes; if an inkblot falls on the page, it remains, a middle finger to the art establishment; there is the feeling Steadman relishes his inkblots.

So will he tell us, please, as one who did a book on Sigmund Freud certainly can, the roots of his rage?

He contemplates, on his back in bed, drinking his Bud.

"I have a gentle mother and a passive father . . . an older sister, four years older, she looks like Maggie Thatcher, she thinks like Maggie Thatcher, I am the antithesis of my older sister . . . I think it's just the thing I told you . . . I like people very much, and yet I hate the human race . . ."

His father, the son of a Lancashire cotton mill manager, wanted to be a mechanic, but didn't do it because Steadman's grandfather felt it was below his station; ultimately, he became a traveling salesman. Steadman's mother was a miner's daughter. Steadman was a restless child: "My eternal cry was 'What can I do, What can I do?' "

The monster of the piece was outside his family: a headmaster Steadman encountered at age 11. He was dreadful, says Steadman, with feeling; a sadist, who would cane and humiliate people in front of the class. In an attempt to escape, Steadman "became obsessed with aeromodeling . . . they gave me flight, they gave me escape."

"That was when I started drawing," says Steadman. "That was also where I learned to fear authority and why my pictures come out the way they do. I get butterflies in my stomach when I draw the military or police . . ."

So if we were to put a finger on it, the source of this rage.

"How the ---- should I know finally where it comes from?" he says. "Except that it continually burns me and I really can't draw unless I'm angry and that's unfortunately why one gets drunk, you try and crank it up . . .

"People who makes drawing are in some way beggars out in the street. Which is why I identify probably with the hooker. You're like a beggar if you've got a point of view and nobody likes it, but you've got to do it . . . It takes something to bring a hooker to your room: I was scared, this strange lady, she was cold, she was desperate . . ."

He talks about life in England, of his wife, who runs a nursery school, of the drawings he does free for Oxfam and Save the Children, of his relationship with Hunter Thompson. It is a life, as he tells it, of continuous journeying between calm and terror; "I like to be amongst the sheep in Kent," he says. "Then I get bored and I want to do something."

He feels more alive with Thompson?

"Yes," he says, "but it's not something I want to be around all the time."

He talks of their first assignment together, at the Kentucky Derby.

"There was a horse with a broken leg and they were pulling the horse on his broken leg, and the horse was pushing and screaming in pain," he says. "You asked about outrage . . . how can you see something like that and not feel outrage; you do feel outrage and it's a resonable thing . . ."

He thinks of himself and Thompson, his individual work not withstanding, as a partnership?

"Almost indelibly," he says. "We get on so well, we understand one another . . . he fired the empty cry, the 'What can I do,' he fired the anger for me . . ."

He speaks of their adventures, and his own, the drunken week he and Thompson spent on first meeting; the streetwalker--another streetwalker--he picked up in Paris and took to a fine restaurant, playing hide-and-seek with the waiter when he came for the check, because the waiter had been rude. It's an adventure not dissimiliar to the one in Manhattan; though it ended up with Steadman leaping about the room with his American Express card, challenging the waiter to snatch the card, forcing him to play games.

"The only thing I fear is physical violence," he says. "I would go much further in things, like, y'know, investigation, if I didn't think I would end up with a knife in my gut."

That's why Hunter Thompson, whom he so often refers to as a big man, a fearless man, is a good partner for him?

"Ummmhmmm," he says.

And the attraction to danger?

"That seems to be where the material comes from, doesn't it?" he says. CAPTION: Picture 1, Ralph Steadman clowns with a toothbrush in his hotel room, and his drawing of Leonardo trying out his flying machine Photo by Nancy Kaye for The Washington Post; Illustration; Copyright (c) 1983, Ralph Steadman, from the book "I, Leonardo," published by Summit Books; Picture 2, Ralph Steadman clowns in his hotel room; by Nancy Kaye for The Washington Post