German Gymnasium, 1 King’s Boulevard, London N1 (020 7287 8000). Meal for two in the restaurant, including drinks and service: £130

You’d think, after all these years writing about restaurants, I’d be inured to its occasional stupidities, but I’m really not. The German Gymnasium, between London’s St Pancras and King’s Cross stations, is a case in point. I simply do not understand how the extraordinarily experienced company behind it, D&D London, can spend so many millions acquiring, converting and fitting out the building and yet be so utterly cack-handed when it comes to the food, which, relative to the build cost, is a small expense. The food also happens to be the whole point of the venture.

On the upside, giving all that money to the architects and builders has produced something pretty. The site was London’s first purpose-built gym and hosted indoor competitions in the 19th century. Designed by Edward Gruning in 1865, it’s a monumental lump of old brick, which was allowed to remain upstanding when the space between the two stations was landscaped. Inside, it is now one cathedral-like vault with dark-wood rafters.

This is meant to house a temple to German food. Accordingly, there is a “grand café” at ground level which has about it the air of a Mittel-European terminus brasserie, all curving banquettes and parquet and glowing lamps. Perhaps this is where we should have eaten, though the majority of the menu – various filled rolls, Caesar salads, prawns with garlic and chilli, a hamburger – seemed about as German as my cat. (My cat is not German.)

I wanted to see what could be done with the German culinary tradition, because my experiences of it have not always been happy. I know there’s some high-end version. I have flicked through those glossy pan-European brochures put out by luxury hotel associations, and they always feature a few German places. There is generally a picture of a man in pristine whites sitting in the chintzy dining room of a schloss somewhere deep in the Black Forest, with a pair of tweezers clipped to his lapel and his jaw set like he’s preparing to de-bone a whole cow without getting any blood on his cuffs.

Lower down the market, when I’ve eaten in beer halls and cafés in Hamburg or Munich, German food has been large boulders of roast meat alongside fried potatoes. I have nothing against either, but they are to finesse and creativity what I am to ballet dancing.

So up one of the two huge staircases we go to the more serious restaurant on the gallery, where the lighting is so moody I have to get out the torch on my phone to read the menu. Perhaps I’m just getting old. We flash the beam across the card searching for the obviously German dishes. Potato and leek soup? Nah. Foie gras terrine or steak tartare? Not really. Winter greens with a spiced parmesan dressing? Now you’re having a laugh. Ah, but there’s a “truffled” beef broth with liver dumplings for £7.50. As ever, forget the truffles. It tastes of them not at all.

The consommé is bright enough, and the liver dumplings are OK, though I dread to think what the gross profit is on this dish. Just to cement those margins they charge £14.50 for a lobster salad, which is a very small portion of good-enough lobster left lonely and marooned in the middle of an expanse of white plate, with a few micro herbs for company. It is a salad in the way a single lamb chop is a salad.

But at least these two dishes are reasonably pleasant to eat. Main courses are crash scenes which should be taped off from public view for the sake of the children. A roast cod fillet with a “smoked fish broth” is a salty, slippery mess; the fish is undercooked, the skin a nasty tangle of grey sputum.

By contrast half a free-range duck makes me wish the poor animal had been allowed to stay free. It is completely overcooked, to a point where all trace of moisture has been driven from the flesh. It is dense and heavy, a total waste of animal. Things aren’t helped by a flavourless steamed dumpling, like a lump of soggy polystyrene that bounces between the teeth and red cabbage which has been so over-cooked as to be edging towards a purée. I know a bit about sweet-and-sour red cabbage. It should have crunch and vigour. This has post-traumatic stress disorder.

Side dishes don’t improve matters. Spiced roast butternut squash turns out to be a completely overworked purée with the consistency of wallpaper paste but none of the utility. An order of cucumber salad with sour cream and dill is first forgotten and then, unfortunately, remembered. Cucumber needs to be taken in hand, to save it from being watery and insipid. This is an under-dressed squelch.

And then to finish, the cherry and chocolate pavlova, flamed tableside for two. This is intriguing both for being not in any way a pavlova and also for not being what anyone would call vastly original. A pavlova, however much you muck about with it, is still a curve of crisp French meringue with cream and fruit. It is not a lump of chocolate ice cream and cherry sorbet covered in singed meringue, as the German Gymnasium’s dessert is, because that’s called a baked Alaska. They bring it to the table, then flame it with booze alongside griottine cherries and flaked almonds.

So no, not a pavlova in any way. But extraordinarily familiar to anyone who has visited the Ivy in the last, ooh, 18 years and had the baked Alaska there, made with vanilla ice cream and cherry sorbet, which they flame tableside with booze alongside griottine cherries. Remarkable how these coincidences happen, isn’t it? But look, they’ve been busy, what with all the building work, and getting the lighting to the point where you can only just see your iPhone in front of your face, and sourcing the paintings of Victorian bodybuilders and finding ways to turn cocktails into foams and airs.

Studying the Grand Café menu later, I note they also do sausages and chips: currywurst for £10.50, smoked schinkenknacker for £12.50. On the one hand this is a lot of money for a sausage. On the other, the latter name does have a helpful onomatopoeic quality. Which is to say we left the German Gymnasium feeling we had been utterly schinkenknackered.

Jay’s news bites

■ The real problem for the German Gymnasium is that it’s all been done before, and so much better, at Fischer’s in Marylebone. A part of the same group as the Wolseley and Delaunay, this self-styled Viennese café does herring multiple ways and has a killer schnitzel list. And all of this served in a room that manages high Teutonic camp with a straight face (fischers.co.uk)

■ TGI Fridays has recognised its customers might not actually want to be there. At selected restaurants you can try the Christmas menu while wearing a virtual reality headset which transports you to a Lapland snowfield where you can take the reins of a sled pulled by huskies. Words don’t fail me; it’s just that all of the ones I’d use to describe this would be obscene (tgifridays.co.uk)

■ A sad farewell to Reg Johnson, the driving force behind the highly regarded Lancashire based Goosnargh chicken and duck business Johnson and Swarbrick, who has died suddenly, aged 64. As one friend put it: “He made local national.”

Email Jay at jay.rayner@observer.co.uk

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