If I say the words Oslo Court, the chances are you'll conjure up an icy courtroom in the Norwegian capital where Anders Breivik, the ideologue who read too many conspiracy theories on the internet, is on trial for mass murder. But there's another Oslo Court, a restaurant of wonderfully indeterminate nationality – Ruritanian is how I'd describe it; "like stumbling into Narnia", is how Matthew Norman does – discreetly positioned on the ground floor of an apartment block in St John's Wood, a hop and a skip from Regents Park (not that you'll be hopping and skipping anywhere after their Wiener Holstein).

One of the many wonders of Oslo Court is that it's always full, and yet every diner believes the restaurant is his secret. This week, as reported widely in the press, the Prime Minister was seen eating there with his wife, which means our secret is no longer safe. But then maybe our old view of the Prime Minister as pampered, privileged and out of touch is no longer safe either.

After a bad few months, eating at Oslo Court could be the beginning of David Cameron's resurgence. Certainly, I am now beginning to regard him in a new light. Hitherto, all his attempts to pass himself off as l'homme moyen sensuel – pretending to like crap music, darts, Cornish pasties and pints of Guinness – have failed miserably. His mouth is the wrong size for pasties and you can tell he wouldn't know where to find a treble 20 on a dartboard, let alone hit it. And, anyway, you can't play darts or drink a pint of Guinness while riding a horse. I don't say that eating at Oslo Court proves his ordinariness, because there is nothing ordinary about the place, but it shows an unconventionality and daring, not to say exuberance, we don't normally associate with him. I bet Clegg, who looks suspiciously like a "fine diner" to me – the way the cream settles under the skin is the give away – doesn't have the balls for Oslo Court.

Cameron chose to go there for one of his "one-date-a-week nights" with his wife. There are people who find the idea of a man dating his wife nauseating. But we are nothing if not uxorious in this column, and we applaud him for it. Only fools and scoundrels think a date is something you do with a mistress.

I'd like to know what they ate but probably won't find out. This isn't idle curiosity. When lovers of Oslo Court encounter one another, usually by secret handshake, the first thing they do is enquire as to the other's favourite dish. The menu at Oslo Court is so long that if you go there every day for a year, you won't exhaust it. And that's before you start on the specials which are a second menu in themselves. I recall once noting that the only quadruped not on the menu was North American bison. A moment later, I was offered it as a special, char-broiled, roasted or in a Roma-tomato stew, with a side dish of paprika-baked potatoes au gratin and red cabbage in Shiraz. My wife tells me I made this up but I have witnesses.

Besides, who wants to divide reality from fantasy in such a place? I have said that Oslo Court is Ruritania, but Ruritania is no fictionalised country for me. As a boy, I read Rupert of Hentzau and The Prisoner of Zenda. If romance was ever going to find me, I'd be sporting a duelling scar, Princess Osra would be in a ballgown made of rose petals, and we would dance the hours away in a ballroom painted a palpitating pink, the very colour of Oslo Court. There are even alcoves here, just like those in which, in a broken accent, I would declare my love, the windows behind fantastically draped, more like boxes at the opera than dining tables, where you can watch the spectacle, the swirl of waiters, the birthday cakes coming out – I've counted as many as six on a single night – and the maestro of the dessert trolley, said to be Egyptian but straight out of Ruritanian operetta, whispering into the ears of elderly ladies, tempting them with "my strawberry flan, my crêpe suzette, or just for you, my darling, my double fruit salad with double cream".

When my wife complimented him on the attention he showered on every woman over 80, he expounded his philosophy. "I know how hard it is for them to come out, how much time they spend over their make-up, choosing a dress, putting on their shoes" – me, too, I thought – "so I want them to have a wonderful time."

Did he breathe the joys of a Pavlova into Sam's ear, chit though she is? Did he tell David he was a lucky fellow? Did our Prime Minister imagine he was the dashing Rupert Rassendyll, political decoy, lover of Princess Flavia of Ruritania, instead of a mere functionary of a failing power, caught texting LOL to Rebekah Brooks?

I have, incidentally, a theory about that. What if – humour me: just what if – he knew all along that LOL stood for "laugh out loud", not "lots of love", and didn't want to embarrass Rebekah Brooks when she corrected him first privately at a pyjama party in a stables owned by Jeremy Clarkson in Chipping Sodbury (we don't have to be precise) and then again for the whole world to hear at the Leveson Inquiry? What if LOL – "laugh out loud, ah, if only I could, Rebekah!" – was an explosion of self-derision, the Prime Minister of a once great nation, having to go cap in hand – CIH – to emissaries of an Evil Empire who don't even get his jokes?

Far fetched? I don't think so. Nothing is too much to expect of a man who will date his wife at Oslo Court.