Because the writer is nearly always the invisible hired hand of the movie business, we must tell you B at once that Jay Presson Allen is now the highest paid woman crafting scripts for Hollywood. Conspicuous display of this information will certainly displease her. She does, when pressed, acknowledge that she is in the over-$500,000-per-film class, right up there with such better-known names as Chayevsky and Simon, but she insists that dwelling on the detail is tacky. Jay Presson Allen, a person of great style and taste, has trouble indulging in tackitude.

In 30 years of writing for television, stage and screen, Jay Allen has managed to remain one of the industry's major hidden assets. In fact, she would not be here now, discussing her work and herself with rollicking good humor, were it not for "Prince of the City," No. 14 in Variety's list of top-grossing films. Allen shares the writing credit with Sidney Lumet, the director, and is also executive producer of the film, and she is passionate about alerting the adult world to its existence.

Were she prone to common human anxiety, she would even be worried about its future. In this time of blockbuster cartoon movies tailored to kiddie audiences, "Prince" is an anomaly -- a nearly three-hour long onionskin-layered morality tale of cops and corruption, taken from the Robert Daley book about a New York narc who went underground for investigators. As it is, Allen observes with force and habitual hyperbole, "This is a very serious movie, and it could be the last one for a very long time."

Allen, whose credits include "Cabaret," "Funny Lady" and both the theater and film adaptations of "The Prime of Miss Jean Brodie," sat down to the script for "Prince of the City" with heavy reluctance. She keeps telling people that she doesn't want to write any more. Two years ago, she even signed an agreement with Warner Bros. that allowed her just to produce four movies, all still unmade because they demand sophisticated audiences. Her recent record, meanwhile, raises the question of what she would do if she were really eager to keep her typewriter in high gear.

In the last two years, in addition to "Prince," Allen wrote and produced Lumet's film version of the Broadway hit, "Deathtrap," due for release next spring; did the script for "Never Cry Wolf," a movie produced by her husband, Lewis Allen, and recently wrapped; and turned out the still-unproduced"Verdict," a courtroom drama to star Robert Redford. She is also working on the book for a Broadway musical of "La Cage aux Folles," another Lewis Allen project, and is developing the pilot for "Tracker," which could be a television series.

She says she's tired. A casual observer would never know. The woman behind the desk of her midtown Manhattan office -- a sparely furnished second-floor space over an Indian restaurant which delivers gasps of onion-flavored air -- is a symphony in white linen and black patent leather and looks as fresh as newly picked celery. Allen is 58, a figure of understated elegance and astringent wit. She has beautifully tended hands that never stop moving and a ringing laugh generous to her own and to other people's humor. At odd moments, she seems a casting director's dream of the sassy sophisticates Eve Arden used to play in the movies, but she is smarter and subtler and softer around the edges.

As a trade, screenwriting offers swell pay and diminished psychic rewards. Making movies, Allen points out, "is a collaborative condition in which the writer is seldom, if ever, the 600-pound gorilla. Although you're treated very nicely, in effect you're a factory worker. You have no control over your stuff, no protection for your material."

In his buoyant way, Lumet sandbagged her into writing the "Prince" script. They had first worked happily together in "Just Tell Me What You Want," the comic film of her only novel. From the moment Allen read the Daley book, she saw a movie in it, but the option was already in other hands. When the first effort to produce a workable script failed, she and Lumet pounced.

"I wanted to produce it, and I wanted Sidney to do it because I thought it was echt Lumet. Sidney always wants to do everything the day before yesterday. He said he couldn't do it unless I was writing because I'm quick. I really didn't want to. Sidney said he would do the basic work, the structure and story line.

"I was so anxious to have the film made that I said, 'Good.' In due time, he presented me with 100 pages, and my heart was in my boots. I thought, 'Oh my God, I'm going to have to tell him it's garbage.' But it was wonderful."

Allen took Lumet's story treatment and retired to a high-priced hotel room in Manhattan. (The Allens own a country place in Connecticut with his-and-her studios and a Park Avenue apartment, but in recent years she has worked in rented distraction-free quarters.) Ten days later, days that began at 5 a.m. and seldom finished before 10 p.m., she had a first draft.

As bare statement, this detail is misleading. It is true that Jay Allen types dialogue faster than most people think. But the flow is the result of a mysterious process that begins in saturation, the finale to weeks -- months -- of research and thought. In this case, she could talk to many of the figures involved in the real story and listen to hundreds of tapes accumulated in the undercover investigation. When she was ready to write, the stuff just rolled out of the typewriter in a furious rush, almost as if she could not wait to have the job over and done with.

Allen's speed writing record was the stage adaptation of Muriel Sparks' "Jean Brodie" novella. That took 3 1/2 days, but that was a special case. It ended a year-long block, the only occasion on which she has ever frozen on an assignment.

"It had very much to do with the book. Any adaptation is rape and dismemberment, and my admiration for that book was so profound that I found myself unable to deal with it." Robert Whitehead, the producer and an old friend, had optioned it for her, although he didn't much like the book, and he had financed her research trip to Edinburgh.

Difficult though that year was, it was far from terrible. "I couldn't even reread the book. Of course, I could distract myself. I had a husband and child and a fairly sanguine nature." Guilt finally drove her into hypnotherapy. One day, she started her morning with the autohypnosis exercises her doctor had taught her, rolled a sheet of paper into the machine, typed "Act One, Scene One" at the top and went on to write a play that was a hit on Broadway and in London.

It seemed more likely that Jay Presson would wind up center front than backstage. She spent much of her childhood in the movie palace of San Angelo, a prosperous West Texas town where her father owned a women's department store. An only child, indulged and adored, she was going to grow up to be Ginger Rogers. Toward that end, Allen managed to take the starring roles in school plays, had tap-dancing lessons and even studied with a local Boston-born elocutionist who eradicated the regional whine. In its place were substituted the polished inflections of upper-class theatrical speech. Allen thinks she now sounds like "a fruity old character actress."

At 18, she arrived in New York with some summer theater seasoning and the awful feeling that she had chosen the wrong career. "I was pretty good. I liked the rehearsals, I liked the first week of performance and then I found it boring. So I did what most girls did: married the first adult man who asked me. How could anybody have married me? I was retarded. There's nothing as dumb as a smart girl who's had no experience."

Her first husband was "a very nice man" who owned a ranch in California. The marriage lasted about six years. Back east again, Allen got acting work occasionally to pay the rent and then, as television took off, began writing for Philco Playhouse and other dramatic shows. It was never hard. She understood dialogue, and she had read widely. She had even been a "hired gun" in school, writing other students' English essays for pay.

In 1954, she married Lewis Allen. Their only child, Anna Brooke, was born the following year, and for another seven Allen was happily retired. "People who don't know me very well say I'm a workaholic. It's not true. Sidney is. He wants to work all the time. I don't find it difficult to fill months, nay years, with my family, with reading -- clearly one is a compulsive reader -- with tennis, with travel. There's an awful lot out there, you know."

Whitehead, for whom she had once written an unproduced play, nagged her into trying another. During a delay in staging "Brodie," a purloined copy of the playscript found its way to Alfred Hitchcock, who coaxed her into Hollywood to work on her first movie. The result was the undistinguished "Marnie." Allen more than anyone recognizes the film's shortcomings; she is ruthless in her judgment of her own and her colleagues' work.

Hitchcock taught her how to write a screenplay, but she didn't catch on fast enough for "Marnie." "It wound up being a literary exercise. Some of the problem with the movie was that Hitch became enamored of parts of the script that were not filmic. There were wonderful scenes in it, but it didn't flow like a movie. I saw it years later on television, and they had just cut the hell out of it, and it was much improved."

Since Hitchcock, she has drifted between Broadway and Hollywood. In recent years, the movie business has made more room for women in its executive suites; still, she says, being female in the industry is "not recommended."

"There is -- how not? -- a certain locker-room sensibility and a bonding which one can never be part of. There is no such thing as a woman being one of the boys. What one can do is have a father figure -- in the loosest terms conceivable. It might be someone 20 years your junior.

"I must say that men have been very good to me. There have been three or four -- and I must say, not particularly self-serving -- who have enjoyed giving me a push or a shove or a yank. There are men" -- to name them, she says, would wound those of her friends who don't qualify -- "who like to do that, particularly if they are very, very sure of themselves. They enjoy the talent and the intelligence and the fun."

These associations have been part of her "luck," a word that pops up in her conversation incessantly. She counts herself blessed by good fortune in every possible way, including that she has never been driven by a need to keep working. "I have always been able to say this isn't where I live. I mean this" -- she delicately raps a laden desk -- "is not the center of my life. Now obviously that is also a position that creates distrust. They say, 'How can we count on you?' I only know that I not only make deadlines, I beat them. I'm always available for rewrites ad infinitum. And I have been able to work with almost anybody."

In that context, a cheery fearlessness is probably an immense advantage. Until recently, she worked out regularly at the Kounovsky Center, which teaches a system of trapeze exercises requiring a pliant body and a lot of heart. Not everybody can dangle upside down from a pair of rings in the interests of fitness, but Allen reports with one of her great peals of laughter, "I'm like somebody who's been lobotomized -- I have no anxiety and very little apprehension. If someone will say in a firm voice, 'Fall forward on your head,' I will. Perhaps that's why I work with directors as well as I do."