For these and other reasons, crime fiction has been moving ever closer to the literary mainstream. "And, oddly enough, mainstream fiction has moved more towards crime fiction. There are mainstream novelists who now have murder or crime in their books who didn't before, and who seem to be increasingly intrigued by crime.
"Occasionally I'm asked: `Do you feel that you're dealing in a rather despised literary form?' And it's very difficult to answer that without being conceited- but I have got six honorary degrees as doctor of literature, which I don't think I'd get if I was dealing in a despised form."
All this, and a life peerage as well. Does being a baroness make any difference to her life? "Well" - and there comes down the line what can only be described as a chortle - "it's much easier to get a good table at a restaurant. And it's undoubtedly interesting to have a seat at the House of Lords. I don't go as often as I should, but when I am there I find it rather exciting and interesting."
IT HAS been hailed as her best novel, and maybe it is. It contains many of the ingredients that, since the appearance of Cover Her Face in 1962, have combined to create the particular flavour of P.D. James's Adam Dalgliesh novels.
A starkly beautiful setting: the windswept Suffolk coast. A politely repressed institution that needs but a spark to set it exploding into murderous destruction: in this case, a theological college where the elite ordinands of the High Anglican church are prepared for a high priesthood - celibacy, Latin Mass and all. And Dalgliesh himself, of course: calm, contemplative, a man with his passions under control.
Given the topic of Death In Holy Orders, it's perhaps not surprising that its characters should be concerned with the state of Western society and the fate of the Christian church. What is surprising is the book's insistent, affectionate and lightly mocking focus on the detective novel as literary institution.
One of the priests is "addicted to the women writers of the Golden Age: Dorothy L. Sayers, Margery Allingham and Ngaio Marsh". When one of the detectives speculates about a link between murders being sparked off by a play on the words "leek" and "leak", she is sharply rebuked by a colleague: "For God's sake, Kate, that's pure Agatha Christie!" And as the investigation circles ever closer to a conclusion, Dalgliesh and his team, homing in on a suspect load of laundry, are informed by the eccentric Father Peregrine: "The washing machine is a kipper". Heavens above: at the age of 80, is the venerable P.D. James - gasp - poking fun?
Well, yes. On the phone from Belfast, the author noted for the cool sternness of her fiction comes across as warm, chatty and dryly humorous. When something strikes her as funny, she bubbles over with unvenerable laughter. But she has always seen the writing of detective novels as a serious business.
"I love structure in the novel, and you do have to construct a detective story - so I thought of it as a marvellous apprenticeship for someone setting out with ambitions to become a good and serious novelist.
"And very early on I came to believe, as I believe now, that I could remain within the structure and conventions of the classical detective story and say something true about the society in which we live."
The classical detective story is classic James territory: an island of order and convention in the increasingly anarchic sprawl of contemporary crime fiction. "Crime fiction covers such a wide spectrum, doesn't it?" muses James.
"At one side you've got the sort of cosies like dear Agatha Christie - you know, that little mythical village - and then, at the other extreme, the rather hardboiled fiction which mostly young men, but [also] some women, are writing, almost in the American way. And then there are some crime novels which are very violent - I don't read them myself, but I understand they are.
"And then you've got the classical detective story, which is the kind I write. Which may have violence in it, but is really more a question of bringing order out of disorder, and examining character under the stress and trauma of a police investigation for murder."
Has the classical detective story changed in the past half-century? "Yes, certainly," she says.
"Although the story is still very important, there's far more emphasis now on character and motive, far more psychological interest, far more realism. In the socalled Golden Age between the wars, the ingenuity of the plot was everything.
"Now the method of murder is more realistic, and the police work is more realistic. In the 1930s nobody had any forensic science, and nobody took any fingerprints. I can't remember fingerprints being taken in a single Agatha Christie novel - can you?
"But there's one Agatha Christie in which somebody is trying to make the murdered girl look like somebody else, so her dark hair is bleached blond - and that deceives everybody. But quite frankly, we know jolly well that no sooner would she be stripped for a post mortem examination than everybody would see she wasn't a natural blonde. Agatha Christie would never deal in those gritty realisms: it was a different world.
"The modern detective story is also less positive in its affirmation of official law and order: we now accept that policemen can be corrupt and that corruption can lie at the very heart of the law. We don't have this feeling that the police are always honest. So I think there are ambiguities that weren't there before."
FOR these and other reasons, crime fiction has been moving ever closer to the literary mainstream. "And, oddly enough, mainstream fiction has moved more towards crime fiction. There are mainstream novelists who now have murder or crime in their books who didn't before, and who seem to be increasingly intrigued by crime.
"Occasionally I'm asked: `Do you feel that you're dealing in a rather despised literary form?' And it's very difficult to answer that without being conceited- but I have got six honorary degrees as doctor of literature, which I don't think I'd get if I was dealing in a despised form."
All this, and a life peerage as well. Does being a baroness make any difference to her life? "Well" - and there comes down the line what can only be described as a chortle - "it's much easier to get a good table at a restaurant. And it's undoubtedly interesting to have a seat at the House of Lords. I don't go as often as I should, but when I am there I find it rather exciting and interesting."
The House of Lords. The High Anglican Mass. The classical detective story. Anyone prone to doleful introspection - such as Commander Adam Dalgliesh, perhaps - might say all three are poised on the verge of extinction.
But is P.D. James gratified by the claims that Death In Holy Orders is her best book, or is she planning another outing for Dalgliesh and Co? A bout of laughter punctuates her answer.
"I'd like to be able to say, `Hang on, I've got another one coming,' but I'm not so sure I can at the age of 80. It's a lovely thought. It would be very nice to be able to feel that. It really would." To which you can hear her fans adding a heartfelt "Amen".
Death In Holy Orders is published by Faber and Faber, £17.99 in UK