Let us go back some 70 years to that begrimed period in the immediate aftermath of the Second World War when this newspaper was called the Glasgow Herald and was headquartered in Buchanan Street, a stone's throw from Central Station.

In those far off days, the newsroom was wreathed in smoke and, if you lit a match under a hack's spirit-inflamed breath, it was like igniting a blow torch.

The eminent editor was one Sir William Dunkeld Robieson. The last of his ilk to be knighted, Sir William presided over a staff that was so numerous there were some in his employ he could not recognize let alone name. Nor, it seems, did he know what they all did. One new, naive recruit from south of the border recalled that for his first three months on the paper he did nothing of note other than dine on black pudding and chips in the canteen.

Another lowly employee was named John Watson. Having previously trained as a journalist on the paper, he had by his own testimony "emerged from the RAF as a Flight Lieutenant with a DFC, some distinction as a pilot who knew how to bomb Germans, a wife and child and more or less bugger all else".

Surviving all that Hitler and his henchmen could throw at him, Watson returned to Glasgow and started a magazine. It was called The Glasgow Review which, it would appear, did not thrive. However, its aims were laudable. According to Watson, it hoped to "capture the Renaissance-like feeling in the arts and politics which was prevalent in Scotland at the time... needless to say I had lost my shirt before I could say 'cut'."

Thus burned, Watson set his sights rather lower. Adopting the pseudonym Nat Karta, he began to batter out pot-boilers, the Caledonian equivalent of the pulp fiction of the kind that was all the rage on other the side of the pond. Unlike The Glasgow Review these proved enormously popular. But though they were bought by the barrowload - around seven million of them, it's been estimated, were sold - they soon disappeared from view like snow off a dyke. Indeed, they are now so rare that even the National Library of Scotland, whose primary purpose is to collect a copy of every book published in the United Kingdom, did not possess a copy. Until recently, that is. A month or so ago it acquired seven Nat Karta titles, for which it paid £60 for each one.

Their vendor was Laurence Worms, owner of London-based Ash Rare Books. With decades of experience in the second-hand trade, Worms knows the difference between that which is truly rare and that which is as common as a tadpole. For him, Nat Karta's racy novels are as collectible as signed copies of the Gutenberg bible and a First Folio Shakespeare.

"They may be cheap and nasty pulp fiction but they are genuinely some of the rarest books I've ever handled," he says. "I'm constantly on the lookout for them. One is on sale for a fiver on eBay at the moment but it's missing a large chunk of the front cover."

Recently, he adds, he got a call from an agitated customer in the US pleading with him to sell his secret stash of Nat Karta's oeuvre. Would that that were the case! The truth is that Worms has sold his entire stock and is currently scouring the globe for more, like a prospector for gold newly arrived in the Klondyke. From the sound of his voice, he does not expect get lucky any time soon.

Meanwhile, most of what we know about John Watson is contained in a book called The Mushroom Jungle: A History Of Postwar Paperback Publishing by Steve Holland which appeared in 1993. In the course of his research Holland managed to interview Watson, who told him that Nat Karta came into being in 1949 when he was at the Glasgow Herald. His first book was called The Merry Virgin and was typical of what was to come.

Others swiftly followed with such titles as All The Things You Ain't, Bravely To Bed and A Dame Called Desire, the blurb for which runs: "A story that tears at the very vitals of life; it lifts you to heights of screaming passion, and carries you from first page to last on a torrent of action that is as thrilling as the climatic movement of a great symphony or the kiss of a beautiful woman... Only Karta could create a character who could get into all this trouble between the pages of one book."

It may not have been the kind of synopsis to win a slap on the back from Creative Scotland but the old adage - never underestimate the taste of the reading public - clearly prevailed. Like Barbara Cartland, albeit in another genre, Watson toiled to keep up with demand. As Worms says, "Success was, perhaps all too predictably, almost immediate." The distributors demanded a new Karta title every month with a print-run of 50,000 copies. Eventually, Watson had to engage other writers to help feed the monster he had created. Some of these writers, it may be reasonably speculated, were fellow journalists on the Herald.

Indeed, there came a point when the first chapter of a book was being set in print while the last chapter was still being written. Suffice it to say, Nat Karta was no Franz Kafka. Once Bitten, Twice Bitten, for instance, is prefaced: "Fiery with the passion of white-hot steel he [Karta] brings to his British public a novel as tempestuously exciting as the sight of half-dressed gypsy girl dancing in the dark before an open fire."

The covers were no less spicy. Most featured scantily-clad young women with regal smiles. They also often contained a grainy photograph of the author. He has a moustache and is puffing on a pipe and looks not unlike Somerset Maugham. Whether he is John Watson we cannot be sure. What we do know, however, is that in 1952 Watson sold the rights in the Nat Karta name to a London company which continued to produce books as Heinz does beans. "Churning out that kind of crap was not really my idea of a life fulfilled," recalled Watson, "apart from which there was some faint writing on the wall."

What he was alluding to, surmises Worms, is the growing interest in pulp fiction by local authorities, who were worried at their corrupting influence. The Lady Chatterley obscenity trial, which would remove the threat of prosecution from authors, printers and publishers, was eight years in the future. For an author such as Watson, even dealing in material that seemed pornographic only to the wilfully prurient, there was the real possibility of criminal conviction.

One such author to have his collar felt was the prolific Hank Janson, the pseudonym invented by Stephen Daniel Frances, whose work was the subject of a famous trial in 1954. Janson's fans included the late playwright Simon Gray who recalled how "the titles alone drove my blood wild - Torment For Trixy, Hotsy, You'll Be Chilled - and on the cover a vivid blonde, blouse ripped, skirt hitched up to her thighs, struggling sweetly against chains, ropes and a gag - and in the top right hand corner, set in a small circle, like a medallion, the silhouette presumably of Hank himself, trench coat open, trilby tilted back, a cigarette hanging from the corner of his mouth."

This, then, was the kind of company John Watson and his alter ego kept. Their books were produced to a formula and gobbled up and discarded like comics. Or, for that matter, newspapers. No one knew this better than Watson. Ultimately, he recalled, "I had learned how to control a narrative, and long before my time a lot of good writers had learned their trade at the rubbish end of the market."