Detective Inspector Katie Maguire was promoted to Detective Superintendent as part of a drive by An Garda Siochána to be seen as more inclusive to women, but to say that her promotion didn’t go down well with her male colleagues would be an understatement.

There was still a hard core of misogynists and golf-playing stonecutters who believed that women gardaí were only good for traffic duty, offering sympathy to the victims of violent crime and making coffee.

It was 2001 when I created Det Supt Katie Maguire and even though it was only 14 years ago it seems like another world altogether. We now have Noirin O’Sullivan as Commissioner, and many other women officers in important roles in the Garda, and it seems to me that the force is all the better for it.

I was editor of Penthouse magazine for four years, and I would be lying if I tried to suggest that wasn’t one of the more desirable jobs in journalism. Before that I had been deputy editor of another men’s magazine, Mayfair, and before that a local newspaper reporter.

However, even the most desirable jobs become monotonous after a time. You’ve seen one breast and you’ve seen them both. While I was editing Penthouse I was encouraged to write a “how-to” sex book entitled How To Drive Your Man Wild In Bed. I wrote it in a very anecdotal style, rather than most of the sex guides of the day, which were very dry and medical. It was a massive success and is still in print (except, sad to say, in Ireland, where it remains one of the few books still banned) .

I was commissioned to write even more sex books and began to make quite a good living out of it. After a year or two, though, the bottom fell out of the sex-book market, so to speak. Instead of writing my next sex book, I dashed off a horror novel called The Manitou, about a Native American medicine man returning from the dead to take his revenge on the white man. It was inspired by the pregnancy of my late wife Wiescka with our first son, and an idea that I had gleaned from The Buffalo Bill Annual 1955. It sold half a million copies in six months, and was filmed with Tony Curtis, Susan Strasberg and Burgess Meredith.

That was when I quit Penthouse and started writing novels full-time. My output was mainly horror novels, but I also wrote historical sagas, thrillers and disaster novels. In retrospect I realise that I should have stuck to one genre, like Stephen King, because I lost a lot of marketing momentum by writing so many different types of novel, but it’s no good crying over variegated novels.

When our three sons had flown the nest, however, I decided to try my hand at writing crime novels. The audience for crime is very much wider than it is for horror, and I thought it would be a good idea to develop a series, all featuring the same detective.

At the same time, Wiescka and I decided to move to Ireland. We had visited Cork and Kerry before, on holidays, and loved it, and I won’t insult your intelligence by trying to pretend that the tax advantages for authors weren’t another incentive.

We found a large Victorian house in Montenotte to rent, overlooking the River Lee in Lover’s Walk, with a romantic view of the hills beyond. It belonged to Denis Maguire, who runs the Cork School of Hairdressing, and from him I stole Katie’s surname. Her first name came from Kathleen O’Sullivan, a pretty young journalist I first met when we were young reporters.

Cork is such a distinctive and unusual city that I knew immediately that I had to set my crime novels there. Because its deep-water harbour has attracted so many varied cultures over the centuries, its language and its traditions are unique. Not only that, I could find no other major crime novels that used Cork as a background, and so the adventures of Katie Maguire would be fresh and unusual, to say the least.

My wife and I made friends very quickly, although the woman three doors up always called us “blow-ins”. (Not that we were upset...she called another couple from Midleton “blow-ins” as well, and that’s only nine miles away from Cork). I have to admit that it took a while to understand the accent and some of the terminology and the slang, but these are what make the Katie Maguire books so intriguing to readers who have never visited Cork and know little about its culture.

What I found astonishing was that many Southsiders have never ventured north of the river, and many Norries have never visited the southside. Not only that, the difference in culture and accent between districts that are only half a mile apart is extraordinary. There is that famous “Mayfield Whine” and they say that the residents of Montenotte speak as if they are swallowing a warm potato. Dowcha, boy!

I admit that I tend to exaggerate some of the Cork slang in the Katie Maguire novels, and one or two readers have complained that I make some of the characters sound too “Oirish”. But I have never used words or phrases that I haven’t actually heard being used in pubs or on the streets, and the majority of my Irish readers have been very pleased that I have put Cork on the crime-fiction map.

Cork of course is the Rebel County and I am very aware of its history in the War of Independence. It would be impossible to write a crime novel about Cork without considering some of the political issues. I had several friends whose fathers or grandfathers had served in the IRA in the 1920s, and I have tried hard to make their struggle understandable to today's readers (especially the British).

I have drawn on several other controversial Irish topics, too. For instance, the historic cases of paedophilia by priests; the discovery of hundreds of babies’ skeletons in the grounds of the former convent in Tuam; the wiping of penalty points off licences by certain gardaí; the tens of millions of euros made by cigarette smugglers; and the many so-called “massage parlours” in Cork which are advertised online. A future novel will also be addressing the wave of lawlessness in rural areas which has followed the closure of smaller Garda stations.

My novels contain some highly graphic scenes of brutality, but then murder is extremely brutal, and I don’t see the point of writing about it as if it’s some genteel game of Cluedo. You won’t find any bishops being battered to death with a badger in the ballroom – not in any of my books. When people get done in my novels they really get done, do you know what I mean, like?

The success of the six Katie Maguire novels that I have written so far has exceeded my expectations – White Bones, Broken Angels, Red Light, Taken For Dead, Blood Sisters and Buried. But they simply couldn’t have existed without the main character, which is Cork, and in the larger aspect, Ireland, and all of the fascinating and remarkable friends that we made there.

Blood Sisters is published by Head of Zeus, at £18.99