Having written more than 40 books, Anthony Horowitz wanted to do something different with his Susan Ryeland series. “It’s my attempt to do completely new things in the murder mystery genre,” he says.

What he wrote is a novel within a novel, in which the crime writer of the first novel is murdered and the hero of the second novel finds out whodunnit. The first novel is set in the Fifties, the second in the present. Still with me?

This box of tricks is obviously impossible to televise so Horowitz’s wife, the TV producer Jill Green, told him to do exactly that — and the show, Magpie Murders, the title of the first book, has just premiered in the U.K. on Britbox (with a U.S. release on PBS to follow), starring Lesley Manville as the murder mystery story editor Susan Ryeland and Tim McMullan as Detective Atticus Pund.

The six episodes took him two years to adapt. It is brilliant, not least because Manville is one of our greatest acting talents. Talking to Horowitz — we are in the ritzy Ivy Club in Soho, London — is easy. He speaks in perfect paragraphs and always has something to say. Last time we spoke he stumbled when I asked him a tricky one about woke culture — “F***, this interview was going so well.” This time he has thought it all through. He’s 66 and just accepts that the young are making a different world.

Lesley Manville and Tim McMullan in the TV series Magpie Murders, based on Horowitz’s novel of the same name.

“You get to my age and it’s very, very easy to get set in your ways and say this is the world — the world that we see now is both incomprehensible and it’s different to how it was when I was young, therefore it must be worse. But you have to embrace the fact that all change is for the good.”

I raise my eyebrows at that. “The people who are deciding that change will live with it. If it’s not good in my view it’s good in theirs, and that’s what matters. I think it’s very easy — especially if you’re a television writer, to sit there and say, ‘This isn’t the world as I knew it.’ But the moment you start saying that you might as well stop writing.”

“You get to my age and it’s very, very easy to get set in your ways.... But you have to embrace the fact that all change is for the good.”

Magpie Murders, the show, includes a Black actor playing a village vicar in 1955. This would be unlikely, but Horowitz believes in color-blind casting.

“That is just the way it has to be. I think it is the way that it should be — and you are of course quite correct that it is extremely unlikely that in the 1950s a village like Saxby-on-Avon would have a Black vicar. But if you take that view, you’re going to make a drama now that just simply looks calcified and wrong. You’ve got to have on one hand sociological, or social history accuracy, and on the other you’ve got modern television and what an audience expects. You have to steer yourself to one at the expense of the other.”

He is, however, staying strong when the cancel culture starts censoring writers, notably JK Rowling because of her views on sex and gender. “There is a sense of writers under siege at the moment and that does bother me. JK Rowling is a gold-plated hero in the world who has done an enormous amount for children’s literacy and charity, and she is under attack. Writers must lead the agenda, not be cowed into following it. You must be free to write what you want, and to express the views you want to express without the world falling in on you.”

“Writers must lead the agenda, not be cowed into following it.”

He worries about causing offense and admits there are whole areas that make him nervous — too nervous even to tell me what they are.

“There are moments when I’m writing a character, who might be from a different ethnicity to mine, or a different sex or gender or background. I start worrying about what the reaction might be because it’s so unfathomable. And that is scary because writers shouldn’t be following the agenda, they should be setting it. But that’s not happening anymore. You get writers making extraordinary statements, like Sebastian Faulks who said he would never describe what a woman looked like anymore because that’s objectifying.

“Sebastian is a very clever person. And when he starts saying things like that all writers have to begin to tremble. Lionel Shriver goes to the press and makes statements which are deliberately, it seems, inflammatory. I don’t want to go down that route. My aim is to entertain, to not get involved in spurious and unsolvable rows.”

“JK Rowling is a gold-plated hero.”

But whatever the problems, writing is to Horowitz what breathing is to the rest of us. He has range, writing TV scripts, the Alex Rider children’s novels and plays, even though his first one, Mindgame, was trashed by the critics. Perhaps because of that, one of his forthcoming books — The Twist of the Knife — is about a critic who is stabbed.

Horowitz is nothing if not prolific. Soon there’ll be a third Susan Ryeland book, a TV script of the second — Moonflower Murders — and Nine Bodies in a Mexican Morgue, about a plane crash in the jungle after which the nine survivors start to be murdered.

“The punch line is really innovative. There’s no killer, incidentally. It’s got a little bit of Agatha Christie’s And Then There Were None in there.”

Manville takes a drive in Magpie Murders.

The mention of Christie signals that he is a grateful inheritor of the golden age of British murder mysteries. This is being widely revived, notably by Richard Osman, under the heading “cozy crime”. It’s a category he resists. “The idea, for me, of writing books that are simply throwbacks to the Forties and Fifties is quite uninteresting. So as much as I love the golden age of crime, it’s called cozy because what came after that is blood splatter and rape and pedophilia. I’m not interested in messy violence and harsh realities. I like a sense of nostalgia, but I slightly react against cozy crime as a genre.”

“My aim is to entertain, to not get involved in spurious and unsolvable rows.”

Admittedly, any description of Horowitz’s stories should begin with the words: “It’s complicated.” But Horowitz’s life has been complicated. The family started off rich in Stanmore, but his father was a strange, distant man and his primary school was “an evil place”. He was an overweight underachiever until he went to Rugby School where three gifted teachers brought out the writer in him.

His father died when he was 22 and, it turned out, he had been transferring all his money into Swiss bank accounts. The family was left bankrupt.

“It’s never bothered me. In a way I had a fresh beginning because of that bankruptcy and having to re-mold my own life on my own two feet.”

His own two sons, Nicholas and Cassian, have had no such problems. They set up Clerkenwell Brothers, an advertising and media company, and Cassian is now working with Rishi Sunak. “I know the day will come when somebody writes an article calling me ‘Anthony, father of Cass’.”

We wrap up. “Are we done? Oh good. Phew! Sorry, that phew wasn’t about tiredness, it was because I don’t think I’ve said anything too stupid or controversial.”

Then he goes off to play, at my request, the Ivy Club’s little piano.

Magpie Murders is available to stream in the U.K. on the Britbox Web site. It will stream in the U.S. on PBS this spring. Anthony Horowitz’s latest novel, The Twist of the Knife, will be published later this year

Bryan Appleyard writes for The Sunday Times of London and is the author of 10 books