There’s a great short story by Alexei Sayle in which the narrator feels he has no option but to break up with his girlfriend after he inadvertently leaves an audio-tape running and captures the sound of a typical evening à deux in front of the TV, the barrenness of the exchange horrifying him. Well, this wouldn’t be the case with my marriage, as it’s far too lively — but my husband did once remark that if I was ever put under sound-surveillance by the contemporary Thought Police for any of my dreadful thought-crimes-against-humanity — being pro-Israeli, say, or anti-Catholic — one of two conclusions might be reached. They wouldn’t find me saying anything pro-Israeli or anti-Catholic that I haven’t already written (remember, anything worth doing is worth doing in public) but the first conclusion might be, apparently, that I was just too mad to risk tangling with. And the second that I was ripe for blackmail and could now at last be bent to the will of our Jew-hating, Pope-licking Establishment as they saw fit.

But the Private World built for two, that’s another goblet of nectar altogether. In his brilliant book Games People Play, the swinging Sixties psychologist Eric Berne put forward the notion — I’m just winging it here, as I haven’t read it since I was a nipper — that the creation of a Magic Kingdom was the true indicator in a romantic relationship of intimacy having been established — far more so than sex. And when a relationship is on the rocks, you can tell because the Magic Kingdom shuts up shop toot sweet, leaving the dumpee in a fantasy for one, long before the sex dries up. There can be few things more devastating for the partner still keen than to speak to the disaffected one in "their" language, only to have them look back blankly as if at a stranger and say politely "What?" This is a very strange fact to have to handle about human beings; that we actually find it easier to have sex with someone we don’t much like — or sometimes positively loathe — than we do to make up stories about non-existent people and/or places with them.

Yet we are not consistent on this mind/body dichotomy. (For a change!) While you can divorce your spouse, and would feel quite righteously justified in doing so, if they were to have sex with someone else, you couldn’t make a decent case for sundering the marital bond because you’d recently found out that for the past few months they’d been getting together after work with an attractive colleague and working out in meticulous detail the map and constitution of a make-believe land, talking in a private language all the while. You’d be laughed out of court. But who’s to say it wouldn’t hurt as much?

What the Magic Kingdom has in common with sex, and why we find them both so special and crave them so relentlessly, is that they both, in their way, take us back to infancy. I don’t particularly enjoy saying this, being someone who fervently supports the rights of women on council estates to picket the house of any paedophile or indeed any paediatrician they see fit, but a lot of the things we do during sex, viewed coldly, are extraordinarily babyish as well as being downright dirty, and I suppose this is one of the things that bothers sex-fearers so much about the act. Of course, as is usually the answer in such circumstances, the secret is not to think too much about it — just do it, lots, till the sharp scalpel of the brain is blunted by the brutish instrument of the body. . .

Er, sorry . . . now where was I? Yes, Magic Kingdoms and Private Worlds. Staying with the sex similarities, revealing the pet names we have for our loved ones can be easily as embarrassing as revealing their carnal preferences. I can’t help thinking that it was the beginning of the end for the Beckhams when Posh sniggeringly revealed to a leering Michael Parkinson — the subject of the revelation sitting gormlessly grinning next to her — that her pet name for her husband was "Goldenballs". Though ostensibly worshipful, the disclosure of this uxorial secret seemed to indicate a disrespect for the boundaries of the Magic Kingdom and a willingness to sacrifice its state secrets in return for global amusement, envy and fleeting applause. It was not so much an unladylike act — which are generally quite good things — as an ungentlemanly one, which are uniformly foul. It was something akin to Mr Beckham going on prime-time TV to confirm that, yes, the notorious stadium chants as to where his wife most liked to "take it" were absolutely spot-on.

Knowledge is power, they say — and never more so than letting a third party in on just what you call someone behind closed doors. It’s far more of a betrayal, in my experience, than sexual dissing. If a woman tells her current lover how bad in bed a previous one was, he won’t take any particular pleasure from it. Of course he’d prefer it to her banging on endlessly about how great the ex was, but he’ll generally assume, quite rightly, that sexual history has simply been rewritten by the spiteful nib of the Big Elbow. Also, through a process of unconscious male solidarity, a part of him will be thinking "Hmm, if she talks like this about him now she might well talk like that about me to some other dude if/when we break up. And I KNOW I’m brilliant in bed! So it’s probably rubbish." So he’ll nod and smirk sympathetically, but he won’t encourage you or join in the flaming.

But reveal a previous Private World/Magic Kingdom to your current companion, and a veritable strutting, sneering macho-fest of pushing forward in the dominance hierarchy breaks out. "The clown called you — what? Boy, what was his preferred bedside reading — Beatrix poxing Potter? And he was a — yeah, right! In his dreams!" Just try it — it’s the one thing that busts through all known bonds of brotherhood in a matter of minutes.

I suppose I should do the bold, rule-breaking thing here and reveal my own Magic Kingdom, but no way! Suffice to say that it has been under construction for nine years now and is nowhere near finished. Its cast of characters, and the landscape against which they play out their strange but somehow familiar lives, has broadened slowly but surely down the years, to the point where we sometimes have to ask whether that was "Julie" or "Dan" speaking, or — well, as I said, Here Be Dragonnes. Tell you one thing though — on Valentine’s Day, when Mr Fluffy Bunny declares his love for Mrs Snugglebum en masse, my husband and I look up from our newspapers and smirk savagely, as hardened junkies will scorn "weekend users", before entering once more into our own Magic Kingdom. I just hope we never accidentally tape it, is all — because then, for sure, we’d have to break up.