In his memoir, Quite a Good Time To Be Born, which I've been reading, Lodge traces his literary concern with this topic back to his first, never-published novel, which he wrote at 18. He describes it as including a female character who becomes pregnant out of wedlock and then dies from complications, having refused an abortion which might have saved her life. Lodge showed the story to his girlfriend, who was, he reports, "somewhat shocked by the novel's preoccupation with sexual desire, complicated by Catholic morality and guilt." Their own relationship was entirely chaste, because this was the 1950s and they were good Catholics.
Lodge says the novel wasn't very good. "The medical and gynaecological details are left vague, since I did not know what they might plausibly be." And, taking a critic's view of his own work, he adds, "The flaws in the novel become more and more evident as it goes on and the novelist gets more and more out of his depth in the subject matter."
What he lacked, he soon realized, was enough experience in the world to write good fiction, and he began looking forward to his mandatory two years in National Service, tediously boring and wasteful though he expected it to be (and it was), in the hopes that he could get material for a novel out of it (and he did).
But how then to deal with the illicit? He expressed his dilemma in an unpublished short story whose first paragraph he quotes:
The envelope fell on to the mat with a dull thud, but I didn't hurry to pick it up, being a young writer, still a student and struggling to get work published, and thus used to such a sound. However it wasn't one of my rejected manuscripts, but a large official envelope that wore its embossed crests and other decorations as self-importantly as a general with three rows of medals. The letter inside was from the Apostolic Delegate, and it was short and to the point. "Dear Joe," it ran (my name's Joe). "I am pleased to tell you that the Pope has granted your request for an unlimited right to commit sin for one day in order to get material for your new book. Yours truly, etc."And Lodge says of this, "there was a lesson in it which it took me a long time to recognise: that the best way to treat Catholic hang-ups about sex was through comedy." And so he did.