The Marriott Hotel, 140 Park Lane, London W1 (020 7647 5664). Meal for two, including drinks and service: £100

Here is a lesson in impotence. It doesn't matter how often I bang on self-importantly in this column about how much I hate menu concepts, how they make me want to stab forks into soft body parts. It doesn't matter if I keep repeating myself. I will still be ignored. They just don't care, these people. And so it is that within minutes of being seated at Lanes of London in the Marriott Hotel by Marble Arch we are approached by a waitress who makes "suited and booted" look like part of her job description, and she says: "Can I explain the concept of our menu, today?" Oh God. Clearly it's not: here's a list of dishes, you choose, we bring.

Oh well. I suppose you want to know what that concept is. The Marriott has noticed that street food is now a Thing; that the capital's roads are clogged with reconditioned campervans knocking out stuff that makes sauce dribble down your forearms, some of which is great and a lot of which is stuff in a bap flogged for £6.50. The Marriotts – I want them to sound like an awful dysfunctional couple you once invited round for dinner by mistake – have clearly decided that the only thing wrong with street food is the street bit. Very breezy, streets.

Far better to bring it all inside a room with blaring Now That's What I Call music, windows that appear to have UPVC double-glazing, and bogs that are a country mile's walk away through the Minotaur's labyrinth of a tourist hotel. Hence the menu is divided up between Brick Lane for Indian food, Kingsland Road for Vietnamese, Edgware Road for the Middle East and Portobello Road for burgers and fried chicken because that's all they eat there, poor souls.

There's also a list of haute pub meat dishes, another of fish and a lazy attempt to fob off vegetarians.

As exercises in missing the point go, they don't come much better. The Marriotts haven't just missed the point. They've studied the point, taken a few notes, turned away from it, gone on a long country walk, ended up in a pub, got drunk and woken up in their clothes the next morning with scribbles on scraps of paper from which they have cobbled together a menu.

It's not that all the cooking is truly awful (though some of it re-defines the word). It is more that it presents the opportunity to create a meal that makes no sense whatsoever. It's discord fashioned from calories; it's dinner as curated by Stockhausen. Still, at least I now know that Vietnam's pho does not go with an Indian butter chicken. And none of it goes with a limp fattoush salad. No single kitchen can be fluent in all these traditions.

Vietnamese food is not something you can just turn your hand to, like crochet or housebreaking, as their pho proves. It should be a deep bowl of nourishing broth and noodles and beef. Here it comes in small bowls with two tiny, limp pieces of beef sliced as thinly as tissue paper. The beef stock should have a deep, rich flavour. This just makes us mutter about Bovril and think about how good pho on Hackney's Kingsland Road really is.

We then have a long wait. Silly street-food vans with their almost instantaneous service. They don't have leather banquettes for you to sit on so you can study the wine list with its opening price of £28 a bottle while you wait. Eventually our fattoush salad arrives, with not enough deep-fried pitta bread in it and no hit of zesty sumac. Eating this literally three minutes' walk from the Edgware Road while mouthing the word "Why?" with my mouthful, is an experience that will stay with me.

To be fair the butter chicken from the Brick Lane list is bang on. It's as appallingly over-sweetened and claggy as any version you could find on Brick Lane, where the curries are uniformly dire. Think chicken in tomato soup. The rice is curiously wet, the breads far better. Deep-fried onion rings taste of last week's oil. And whoever wants to dip one in a Marie Rose sauce? I mean it. Who?

There are bizarre inconsistencies. From the "meat" list, devilled kidneys brings deftly prepared offal, still viscera-pink inside, seared outside. I can't find fault with their cooking. The sauce, however, is bizarre. It tastes of sticky demi-glace and red wine. There's no punch from cayenne pepper at all. They are called devilled for a reason; the cayenne isn't optional.

The Portobello Road section offers the greatest high and the lowest low. The latter is a piece of fried chicken, coated in a bright orange breadcrumb case that flakes off like scabs to reveal pallid-skinned hen underneath. It looks like a boulder that has been badly coloured in by a child. It may be half a very small bird. It's hard to tell. Either way the £12 price tag is outrageous. The honey and sesame dressing next to it tastes of sugar, vinegar and low self-esteem.

But then come their sliders, which are glorious and make me hum happily to myself. They are made from braised brisket, reformed and seared and dressed with a little veal jus, and perched inside tiny brioche buns. Alongside is a pot of pokey horseradish cream plus two hunks of roasted bone, the slippery beads of marrow within topped with breadcrumbs. For £7.90 it's also good value. It's when we eat these that it becomes obvious there are people in this kitchen who can cook, as long as it's from their natural repertoire. Instead they have been smothered by a bloody concept. Did I mention how much I hate concepts?

The kitchen's skills become even more obvious at dessert. Poor Knights of Windsor sounds like a rowdy bunch of mercenaries from Game of Thrones. It brings crisp-fried eggy bread with honey-glazed apples, a Calvados ice cream and a jug of custard. Jammy dodgers served in their own cutesy tin are shamelessly crumbly shortbread biscuits sandwiching strawberry mousse with, on the side, a glass of chilled strawberry liquor. These desserts almost banish the memory of the strangeness that has gone before. But not quite.

It's pleasing to imagine the Marriotts might eventually come to their senses. The problem is they've embossed the name of the restaurant into the front step in brass. They came up with a concept. And now they're stuck with it.

Jay's news bites

■ For proper devilled kidneys, head to the Farmcafé on the A12 at Marlesford. It's essentially a roadside caff, but one that takes its food very seriously, especially when it comes to breakfast items. Then again the pickings round here – Suffolk is famous for both its pork and smoked products – are rich indeed. The full breakfast costs £6.90 – kidneys extra – but will set you up for the day. Afterwards you can browse the farm shop next door (farmcafe.co.uk).

■ I try lots of new products. Few have made me widen my eyes in appreciation more than cock scratchings made by a young chap called Ed Jones: deep-fried chicken skin, salt, pepper and that's it. Well what did you think they'd be? They're available at the dozen or so branches of the independent bar chain Brewdog (brewdog.com).

■ Closure news: serial restaurant entrepreneur Alan Yau has shuttered his rather odd pan-Asian café Naamyaa in Islington, London. No matter. He has new places opening this year including a "Chinese gastro pub" encouragingly named Duck and Rice.

Email Jay at jay.rayner@observer.co.uk. Follow Jay on Twitter @jayrayner1