Rennie Airth is currently five books into his trilogy of historical mysteries. Yes, you read that correctly. This South Africa-born journalist turned fictionist set out, in the late 1990s, to pen just three novels about early 20th-century Scotland Yard inspector John Madden, his family, and his police colleagues. But as the now 81-year-old Airth explains, “I found I had more to say about the Maddens and the people around them. They had come to fascinate me and I wanted to know how they would continue with their lives. It’s curious how one’s characters take on a life of their own, but they do.”

Madden made his entrance in River of Darkness (1999), a persistently surprising whodunit set in the south of England in 1921. He was described as the son of a farmer and a longtime member of Scotland Yard, who’d left the force “some years before” after losing both his spouse and baby daughter to influenza, and then taking up arms in the battlefield trenches of World War I. Once the shelling and bloodshed were done, Madden returned to the employ of London’s Metropolitan Police, but he was “a different man from before,” Airth wrote, “a tall grim man with a scarred forehead…more like a monk than a policeman.” River of Darkness found Detective Inspector Madden hunting the slayer of a well-to-do family in Surrey, an evasive malefactor who may have been responsible for other unsolved crimes as well, and whose tactics brought Madden face to face again with the combat horrors he’d witnessed. An outstanding addition to the field of World War I–associated mystery fiction, River of Darkness won France’s Grand Prix de Littérature Policière for best international crime novel in 2000.

Half a decade later, a sequel finally found its way into print: The Blood-Dimmed Tide. It imagined Madden—now retired from the Yard and living as a farmer in Surrey with his physician-wife, the former Helen Blackwell (introduced in River of Darkness), and their two offspring—being called upon in 1932 to join the pursuit of a sexual predator targeting children. Airth’s fans were left to wait patiently once more for what had been announced as the concluding entry in Airth’s trilogy, The Dead of Winter (2009)…only to then be rewarded for their loyalty with an unexpected and quite exceptional fourth Madden yarn, The Reckoning, released in 2014. Each new book in this series has skipped forward more than a few years at a time, with the events rolled out in The Reckoning taking place in 1947, after the end of World War II.

Now comes The Death of Kings, Madden’s fifth investigative outing. In its pages we see Airth’s protagonist, in 1949, re-examining the 11-year-old fatal strangling of an opportunistic actress, Portia Blake, after a jade pendant—missing from her body when it was discovered on the country estate of Sir Jack Jessup—is suddenly mailed to police. It comes with a cryptic note suggesting the original inquiry into Blake’s murder had failed, and that the itinerant farmworker who confessed to the crime and was executed for it, was innocent. Working amid the forbearance of police officials wary of his meddling, Madden revisits the events surrounding Blake’s demise, quizzing her then fellow guests at the Jessup manor and provoking suspicions about Stanley Wing, a Eurasian entrepreneur short on scruples but perhaps long on links to Chinese underworld figures interested in gaining influence in Britain. He’s aided in his efforts not only by Sir Jack’s heir, Richard Jessup—a gentleman to whom Madden takes a quick shine—but by his blonde “knockout” of a daughter, Lucy Madden, who proves to be both magnetic and unpredictable. Like previous Madden procedurals, this one strikes a comfortable balance between being a puzzler and a character study, and illuminates nicely how preconceptions can have an impact on crime solving.

Preparatory to writing this piece—my final column for Kirkus, after a rewarding, almost six-year run—I asked author Airth a number of questions about his new novel and his history as a wordsmith.

Did you grow up wanting to be a writer, or had you other career expectations?

I did think about being a writer from quite an early age and never really considered any other career possibilities, other than journalism.

In the mid-1950s, you moved to England to work as a foreign correspondent for the Reuters news agency. When and why did your interest in journalism begin, and did you study journalism in South Africa before leaving there?

I was 20 when I left for England—it must have been 1956—and the first job I got there was with United Press as it was then (now United Press International). Prior to that I worked for a couple of years on the Star newspaper, in Johannesburg, learning my trade. In those days, one didn’t study journalism as a subject—at least not in South Africa, and not in England either—one joined a newspaper as a so-called cub reporter and learned the job that way. After spending a year with United Press, I joined Reuters.

I understand that you were inspired to create the first John Madden novel, River of Darkness, by a family scrapbook focusing on your uncle, who was killed during World War I. What was that uncle’s name, and do you know much about what happened to him during the war?

Yes, coming across the scrapbook played a major part in my decision to write the first Madden novel: that and the fact that I had been reading a good deal about the Great War, as it used to be called. The scrapbook had been compiled by my grandparents to memorialize their elder son, who was killed in action. His name was Rennie, and some years ago I paid a visit to the cemetery in Belgium where he is buried and saw his name (and mine) on the gravestone. He had served in the trenches for two years before being posted to a desk job in Boulogne [France]. Reading between the lines, I believe his nerves were probably shattered, but such was the desire by young men at the time not to shirk what they felt was their duty, that he volunteered to be an observer in the Royal Air Force, taking photographs of enemy positions. He duly qualified and was posted to a squadron, but on his first mission the plane he was in was hit by ground fire and he was seriously wounded. He was still alive when it landed, but died before reaching the hospital. My father, who also fought in the war and had the good luck, if I can call it that, to be captured, never spoke much about his brother or his own experiences in the trenches, and I’ve sometimes wondered if he suffered from a kind of guilt at having been the one who survived. But he did tell me that Rennie had been a very good cricketer at school.

Madden starts out in your series as an ex-soldier left very much alone by the deaths of his wife and baby daughter, and having returned to detective work “a different man,” intensely devoted to crime solving. However, by the time of his second adventure, he has already retired from Scotland Yard, remarried, and started a second family. What led you to accelerate Madden’s life in that way, rather than allowing readers to see him continuing as a police detective, at least for one or more novels?

I’ve written the Madden books in this way—I mean leaving intervals of time between them—because I didn’t want to be trapped in the kind of series familiar to mystery readers along the lines of “another case for Inspector Madden.” I also wanted to write about the changes that came about in middle-class society in England between the wars; and later about the further changes brought by the Second World War and its aftermath. Having Madden leave the police force for an ordinary life in the country and then be drawn back intermittently to tackle a case seemed the best way of going about it. Thinking up believable ways of contriving this has been one of the challenges in writing these books. But I never saw him as “intensely devoted to crime solving,” as you put it, even though he’s an unusually talented investigator. Returning to his work at Scotland Yard was a way of blocking out his memories of the war, as I explained. But he’s a complex man and above all one who feels an obligation to others, so when he’s faced anew with the challenge of trying to track down a killer, he doesn’t shy away from it. As for the rest, meeting [his future wife] Helen was the crucial event in his life following the first war, and I wanted to give full play to that and make its meaning for him clear to the reader.

Every one of the Madden novels has its strengths. But what do you see as the specific assets of The Death of Kings? What were you hoping to accomplish here that you had not achieved in this series’ previous installments?

Each of the Madden novels has a particular theme. In River of Darkness, he was a detective doing his job, though much resulted from that; in The Blood-Dimmed Tide he was responding to a feeling of obligation after being the one who happened to find the body of the murdered child; in The Dead of Winter it was the murder of a young Jewish woman who was working for him as a land girl that prompted him to help in the investigation; in The Reckoning he finds himself dragged into the case almost against his will and for the simple reason that although he is clearly involved in it, he doesn’t know why and wants to find out. Now, with The Death of Kings, he starts by simply doing a favor for his old friend [and former chief inspector] Angus Sinclair, who is laid up with gout and wants an old case of his looked into. But in the course of the story, Madden makes a new friend in Richard Jessup, and it is this relationship which develops into a close bond that lies at the heart of the tale.

I imagine you must have done considerable research before writing River of Darkness, especially since you had to know something about Scotland Yard’s operations in the early 20th century. But how much study is required in preparation for each new Madden tale nowadays?

I did quite a lot of research for River of Darkness because I wanted to get the period right, but for the later books I’ve done less since in a way I’m familiar with that time, mainly from reading. I’ve never had to do deep research. What I’m after always is the flavor of the period and that’s best served by paying close attention to the way my characters behave towards each other and how they speak. It was a more courteous age, at least among the middle classes, so I’ve steered clear of four-letter words, which have now become almost the only form of emphasis with so many writers (and feel all the better for it). More than once after writing a bit of dialogue, I would ask myself whether my father would have put it that way. So I’ve always had that to fall back on.

One of the distinctive things about The Death of Kings is that you have incorporated into your plot the criminal underworld of the Chinese Triads. Surely, that demanded a good deal of investigation on your part. Were Chinese criminals really as present in 20th-century London as you suggest?

Yes, I got interested researching the Triads with their strange hierarchy and weird rituals. But the information, at least at the level I was concerned with, wasn’t hard to come by. It’s all there on the Web. You ask whether these Chinese criminals were really present in 20th-century London. I think they were there, though in small numbers, as early as Victorian times. They only became more of a presence when the drug trade took off in a big way. There was a big Triad presence in Amsterdam because of all the opium entering Europe through Rotterdam, and later the drug trade spread across the Channel. I don’t know whether people were actually executed in the dramatic way I showed, but like the Mafia anyone deemed to have betrayed the family could expect little mercy, and I would hazard a bet that’s still the case.

Also interesting is how Detective-Constable Lily Poole has influenced this series. Introduced in The Dead of Winter, she seems both capable and perceptive. But other than as a symbol of how the old-boy network of British policing was changing after World War II, what do you see as her importance to the series?

I decided early on that I wanted a young woman detective to feature in the series, but I couldn’t introduce her too soon for the simple reason that although there were a handful of women working in the CID [Criminal Investigation Department] between the wars, they were nearly all restricted to dealing with so-called domestic cases, and I wanted Lily more involved than that. She has had to battle to get where she is, and besides shining a light on the sexism that permeated the Metropolitan Police, I felt she would bring fresh life into the series. And she has proved to be more than up to the job. As Chief Superintendent [Charlie] Chubb notes in the latest book, she shares with Madden the gift of being able to sense “how the dots are joined up.” She’ll continue to shine.

You now live in Italy, but have you been back to South Africa to see how that land of your birth has changed over the last eight decades? What do you think of its evolution?

Yes, I go back regularly to South Africa to see my sister and other members of my extended family and of course it has changed enormously, thanks to the end of the apartheid regime. They’re far from solving all their problems, and I’m sorry to say both crime and corruption are flourishing. But whenever I go there I sense a great deal of energy that seems to me to have been released by the free mixing of races, which was absent in the bad old days when “whites only” was a sign you saw everywhere. So all in all, I’m optimistic about the future.