IF I’m honest, reading the first few chapters of his new book Dead Men Whistling the thought did cross my mind that Graham Masterton is losing his edge these days.

OK, yes, it does open with an officer of the Garda Síochána in Cork having his head chopped of with a chainsaw and then a tin whistle inserted into the stump. And to be fair, he’s not the last Cork policeman to suffer the same fate in the course of the book. And each decapitation described in eye-watering detail (“Next, the teeth bit into his vertebrae”)

But even so, by Masterton’s standards, this is non-alcoholic compared to the full-strength horrors the author has given us in the past.

“I have calmed down a bit,” Masterton says when I suggest as much. “The sort of things that happen in real life make the sort of things I write about pale in comparison. They really do.”

Hmm. Maybe we should take that under advisement. Because it’s hard to imagine real life ever matching the warped imagination of Masterton over the years. Since the early 1970s the Edinburgh-born, Epsom-based author has written more than 100 books ranging from crime fiction (in the shape of his current Katie Maguire books, of which Dead Men Whistling is the ninth) to historical sagas, and from sex manuals to, most infamously, horror novels.

And in all of them, Masterton goes the extra mile. And then a bit further.

“To my mind there’s no point in writing a crime book that isn’t graphic and explicit,” he says. “I’m not Agatha Christie. The worst thing that happened in an Agatha Christie book is that the bishop would get beaten to death with a badger in the bathroom.”

If Masterton was to write that book the badger would be at least rabid. And possibly possessed.

In Paperbacks from Hell, a recent and often hilarious history of horror fiction in the 1970s and 1980s, author Grady Hendrix singles Masterton out as one of the wildest writers in the genre.

“Critics write reviews of Masterton’s books in a stunned, slack-jawed daze,” Hendrix notes. “Wherever you think this book won’t go, Masterton not only goes there, he reports back in lunacy-inducing detail.”

He cites numerous examples which include - and best skip this paragraph if you are of the nervous disposition - cannibalism, amputee assassins, flaming dogs and explosive vomiting. Oh, and a giant mutilating the genitalia of a renowned psychic. You don’t get that in Anita Brookner novels.

The fact is, Masterton has no interest in allusion and mystery. He never leaves you in doubt about what is happening in his books. He always shows and tells.

 “The challenge,” Masterton tells me when I bring up the extremity of his books, “is of course to see how far I can take it.”

The question is why though? Why do you nail your characters to the wall (often literally) in your books, Graham?

“I’m not entirely sure. I think there’s an element of entertainer in me. And I do like to shock people a bit. There’s a lot of extreme stuff in the Katie Maguire books, but they’re still selling well to people of both sexes. Or all sexes, we should say these days, shouldn’t we? They seem able to accept it.

“People do like to be shocked. They enjoy it. That’s the whole purpose of horror books. You read a horror book to get that frisson of fear. And at the same time, deep down, you know that you are quite safe.”

Has he ever horrified himself with anything you have written? “No, I can’t think of anything.”

In fact, he says, given all the appalling, twisted things he has imagined in his books the most extreme reaction to anything was when he wrote a scene in the late Katie Maguire book in which Katie’s dog was terribly injured. “I got an absolute torrent of emails saying: ‘You can’t let Barney die.’”

Canine fans might like to know Barney is still alive in Dead Men Whistling. As for all the humans in the book … Well, I’m not promising anything.

It should be said that Masterton has himself survived to the grand old age of 72 without ever having his head cut off, been torched by flame-throwers or eaten by gourmet religious cults. But his has still been a richly storied existence, one that takes in everyone from William Burroughs and Bob Guccione to Barry Sheene’s girlfriend, and everything from seventies sex magazines like Mayfair and Penthouse to Hollywood movies.

But let’s start it in Edinburgh. Masterton spent the first three years of his life in Morningside, the son of a Royal Engineer. “My grandfather was John Masterton who was His Majesty’s Chief Inspector of Mines. A number of my other relatives fell down mineshafts,” he says in passing, one of the many “what the …” details he throws out in our conversation.

It does not sound like a happy childhood. Masterton’s own father was something of a martinet. “He liked shouting at people. At me too. I’d get my nightly smack.”

Perhaps no surprise then that his parents separated when he was young, by which time Masterton was living in the south of England. As a teenager, he was expelled from school in Crawley when, “instead of studying Shakespeare and Byron, I started studying Jane and Jill.”

This turns out to be something of a recurring pattern.

At 17, he got a job in the local paper. Four years later, having failed to get a job on Fleet Street, he wrote a “very arrogant letter” to a new men’s magazine called Mayfair, wangled an interview at the RAC Club in Pall Mall and was offered the job of deputy editor.

In an age of internet pornography, the idea of the top-shelf magazine is rather quaint these days (we’ll get to the politics of it a little later). But back then they were a new phenomenon. Basically, from my own teenage memories, they were a combination of photoshoots of naked women and articles about cars.

What did the job of deputy editor of Mayfair entail anyway, Graham? “I had to write the letters,” he begins. Wait, you mean, the readers’ letters weren’t real?

He carries on as if that should have been obvious. “And some of the articles. Of course, the worst thing I had to do was interview all the girls. I would have to go up to the studio and have a chat while they were being photographed. I can’t tell you how difficult that job was. I talked to the girls about why they wanted to appear in the magazine with nothing on.”

And why did they? “Well, most of them were proud of their appearance. And, of course, we paid quite well. There was nothing sleazy about it.”

After a few years at Mayfair (where he eventually became the editor) he fell out with his boss, didn’t turn up for work the next Monday and rang Mayfair’s competitor Penthouse. They gave him a deputy editor’s job.

“Mayfair had been a bit more stuffy. The editor there wanted Mayfair to be rather like a gentleman’s club, whereas Penthouse was run by Bob Guccione; gold chains, chest hair and all of that. We were all very groovy at Penthouse.”

Guccione, he says, had huge charisma. “Everyone on the magazine except me was scared of him. I liked him. He was OK, but like a lot of people like that who have a lot of sycophants around him, he sort of disappeared up his own rear end.”

Still, it was fun while it lasted, Masterton says. He had a decent budget and could hire writers he admired. “Kingsley Amis wrote our wine column and JG Ballard used to write for us.”

Of course, how many of its readers were buying it for the articles is possibly debateable. We can’t rewrite the sexual mores of previous eras, of course, but I wonder how he looks back on those years now. Does he worry about the way those magazines patently objectified women? “No,” he says. “Penthouse was probably the most feminist publication you could find.”

Hmm. That might be news to Spare Rib.

“All the girls were always treated as equals,” he continues. “The advertising manager was a woman. There was never any leering or any of that.

“We were good friends with most of the girls who appeared in it. I was friendly with Stephanie McLean, a gorgeous girl. She married Barry Sheene.”

This prompts a reverie. “He remembers one particular layout they did with McLean. “We hired a crypt under a church in Oxford Street. Stephanie lay on an altar wearing a black PVC bustier while a dwarf stood over her with a whip.”

Actually, that sounds like it could be an out-take from one of Masterton’s later horror novels.

“We did a fashion shoot based on leather coats,” he continues. “We went up to Wimbledon Common dressed as Nazis in a motorcycle and sidecar. You could do things like that in those days.”

It’s possibly worth noting that we’ve rather wandered away from Masterton’s feminist thesis here, I fear. Never mind.

Who was the younger Masterton back then, I wonder? A well-dressed Mod, he says. A lover of Beat writing. Oh, and friendly with William Burroughs. “He came to London to live and I used to go and visit regularly. We just spent whole evenings having dinner and talking about writing.

“One day Allen Ginsberg turned up. I was sitting there, and Allen was saying: ‘I’m so tired, man.’ And he lay on the floor and he put his horrible, greasy locks all over my lovely Italian pale suede shoes. So, regardless of the quality of his poetry, I’ve hated Alan Ginsberg ever since.”

Whilst at Mayfair, Masterton was encouraged to write sex manuals - which he did initially under the name of Angel Smith. Angel even got fan mail. Or she did until a jiffy bag containing a used condom turned up.

“After that, I wrote all my books under my own name. I wrote How to Drive Your Man Wild in Bed which sold about half a million copies in six months. It’s still on sale.”

But by the mid-1970s the bottom had fallen out of the sex books business (boom boom) and with one book left on his contract he decided to turn in a horror novel. His wife Wiescka, whom he had met when she was an editorial assistant at Penthouse, was pregnant at the time and, duly inspired, he wrote a story about a woman pregnant with Native American spirit called a Manitou.

The resulting novel was quickly turned into a Hollywood movie starring Tony Curtis. “I got a lot of sales in the Native American reservations. I was taken to lunch by Sitting Bull’s grand-daughter.”

Masterton hasn’t stopped writing since. If anything, he is writing more now. “My life is mainly working,” he admits. His three sons are all grown up and Wiescka sadly died in 2011.

“I see people whose partners die, and they seem to get married two or three years later. I’m not ready for that yet. But I’ve got an awful lot of female friends and they give me the female company I enjoy. They’re all a lot younger than me.

“Sometimes my sons say: ‘Dad you’re going out with somebody younger than my wife.’”

Unlike many of his characters, there is plenty of life left in Graham Masterton.

Dead Men Whistling, by Graham Masterton is published by Head of Zeus, priced £18.99.