Traitors Gate.

"AN incredible three million copies of her books have been sold in America," boast Anne Perry's British publishers. Incredible, no; if they say so, I believe them. A bit puzzling, yes; the reason for such popularity is not altogether clear. But the op- erative word in that boast is "America." Although Miss Perry is a British writer, living in Britain, her books are much less well known on the eastern side of the Atlantic. And that's not puzzling at all.

Her novels, set in Victorian London, are -- like those of Martha Grimes, an American mystery writer who has set nearly all her books in Britain -- full of slight solecisms and anomalies liable to set sensitive English teeth on edge. They have been praised by the upmarket American press for their historical authenticity and atmospheric plausibility but authentic and plausible, to anyone with the slightest knowledge of the period, they are certainly not.

Miss Perry's books fall into two, scarcely distinguishable, series, both featuring police detectives who pursue their investigations through foggy streets to the clip-clop of hansom cabs, from the drawing rooms of Mayfair to the stews of Limehouse. In the latest, Cain His Brother, ex-Inspector Monk (now an "Agent of Inquiry," long before Sherlock Holmes claimed to be the only "consulting detective" in the world) searches for a missing man in the fever-ridden slums of the East End. His quarry, a saintly character, had an evil twin brother, who may have murdered him: but there is no body, and the villain is quite confident that none will be found. A trial ensues nevertheless, with a melodramatic denouement.

The mood is gloomy throughout, and, squalor being squalor, well-founded in sociologically inclined history books. So far, so plausible -- until the narrative moves into the more socially complex regions of the Bar and the professional classes, where it suddenly becomes apparent that the author does not know what she's talking about. London barristers don't have "offices" in a street near Lincoln's Inn Fields: they had, and have, chambers in one of the Inns of Court. They don't "approach the witness stand" like Perry Mason. Nor are English clergymen called "Reverend Wyndham" -- or, at least, they weren't before Hollywood's influence.

In all Miss Perry's books, modern prejudices, particularly about class and the position of women, are constantly insinuated and heavily emphasized. Victorians, however radical, simply didn't think in those terms. Gentlemen, she tells us, "only dabbled, they did not actually work"; which would have astonished some very energetic Victorian gentlemen. As for women, they were "the weaker vessel, expected to weep, to lean on others"; which would have amazed many tough-minded Victorian ladies. On the other hand, no respectable Victorian man would ever have said "what the hell" in the presence of a lady. Still less would a respectable woman have used such language herself ("bloody incompetent generals").

The most recent book in Miss Perry's other series, Traitors Gate (why no apostrophe?), set in higher social circles, was even more liable to such solecisms. In it Superintendent Pitt, aided by his wife, Charlotte, investigates a murder in a gentlemen's club. The crime involves Important People: it touches on the colonial struggle for Africa and a sinister anti-democratic conspiracy, the Inner Circle.

Miss Perry has conscientiously studied the background details. She knows London's street plan, what songs were sung in the music halls, what fashions the ladies wore: and she makes sure we know she knows. The effect is spoiled by things in some ways less obscure but perhaps not quite so readily swotted up. The club she writes about, crucial to the story, has a "manager" and "stewards," like an American club, not a "secretary" and "waiters"; it has a "foyer" and a quite impossible inner room for senior members only. The club's domestic arrangements are important because they affect the solution, described as "very clever and very efficient" but in fact absurd.

Even that sort of thing might not matter if the Victorian feel were right. There are some other curious Americanisms -- "As close to Westminster as we live" (no Englishman, now or then, would insert the first "as"), "French doors" instead of "French windows," and (admittedly not often) some hilariously dreadful dialogue --"Must be damned urgent to seek a fellow out at his club, what?" When a high flyer at the Colonial Office is described as academically outstanding because he graduated from Cambridge at age 23, one can only ask what took him so long. Again we have the word "bloody" used in the presence of, indeed addressed to, a lady.

Has Miss Perry never seen Pygmalion? Has she never read Victorian novels -- Trollope, Wilkie Collins, The Dolly Dialogues, The Four Feathers, or even the Sherlock Holmes stories? Or another, equally famous, Victorian tale which had better not be named for fear of giving away the twist at the end of Cain His Brother? The surprising answer is "Possibly not."

A glance at her biography, as given by the publishers, reveals that, although seemingly a conventional middle-class, middle-aged Englishwoman, she grew up in New Zealand, worked for a while in California, and now lives in a remote Scottish village. But that's not all.

While Traitors Gate was in preparation a movie called Heavenly Creatures was released, about a forty-year-old case, famous in New Zealand still, in which two young girls, for psychologically obscure reasons, battered to death the mother of one of them. A New Zealand reporter somehow got on the trail of Miss Perry. When asked, she immediately admitted that she had been one of those girls, though not the one whose mother was murdered. She had served five and a half years in a women's prison, was released at age 21, returned to England, where she had been born, and changed her name.

She claims to remember little of the murder and to have long ago lost touch with the other girl. She has never denied her identity but, naturally enough, doesn't like talking about it. She has become a devoted Christian. But she did miss out on a good deal of education.

The publicity that followed the revelation has been handled not so much discreetly as carefully, with well-controlled articles and interviews. Everybody on both sides of the Atlantic who is at all interested in her books now knows the facts. Despite her initial unsophisticated fear that her publishers might drop her if they knew, the story has predictably helped, not harmed, her sales.

All credit to her for making a new life and a successful career. However, I cannot help feeling, as she probably does, that it would be better, from a literary as well as a personal point of view, if we didn't know. People reading her books are now bound to ask: "Can you tell?"

The most spectacular parallel instance is that of James Morris, who underwent a highly publicized sex change while writing his (or her) trilogy about the British Empire. Nobody can read those excellent books now without trying to see the join, the point where the sex change happened. But there is no perceptible join. Nothing alters.

This provokes a much broader and deeper question about authors in general. Which is the real person -- the one whose apparently intimate acquaintance we make on the page, or the frequently disappointing figure whose hand we may shake or whom we may see blathering on a television talk show? How do we feel about a woman protagonist, perhaps narrating in the first person, created by a male author -- or the other way around? Would we feel differently were we unaware of the author's sex?

Are the currently fashionable courtroom thrillers distinctly better for being written by lawyers? Or romans policiers for being written by policemen? Erle Stanley Gardner was a lawyer and Dashiell Hammett had been a private eye, but they both learned more from working on Black Mask than from experience in the field. Carroll John Daly, the first begetter of the hard-boiled thriller genre, was rather a nervous man who once thought he should carry a pistol to see what it felt like -- and was promptly arrested. Mystery fiction need not be realistic; realism is not the point.

The same applies to espionage fiction. Some writers of good spy stories did have experience in intelligence work, but you would never guess it from their unrealistic tales. Yet John le Carre's not very happy time in the British Secret Intelligence Service provided the pungency of his novels. And the Rumpole stories would be much less fun if John Mortimer were not so familiar with lawyers and judges.

So which is the rule and which are the exceptions? Truthfully, there is no rule. Trying to deduce one leads only into what le Carre calls "a wilderness of mirrors." Homer and Shakespeare are enhanced, not diminished, because we know so little about them. Anne Perry's work would lose nothing if we knew less about her.