Barbecoa is Jamie Oliver’s new restaurant on Piccadilly, and no matter how many times I mutter the name, I do not know what it means, if it means anything; it may be a posh riff on barbecue, which does not need gentrifying, because barbecue is cuisine’s mass murder. The only other mention I can find is the original Barbecoa in St Paul’s. This is Barbecoa 2, then: the sequel.

I used to like Jamie Oliver, or the idea of him. I liked his willingness to be a spokes-chef; to damn parents who feed their children Turkey Twizzlers and roof insulation; I liked that he is fat. Then I ate at Jamie’s Italian in Soho and met a plank resting on two tins of tomato paste bearing greasy salami and cold cheese, and steak frites that thought they were Italian, and I stopped liking him.

I began to think him cynical and money-grubbing. There is a peculiar depravity to the mid-market family restaurant in central London that offers bad value through a good name, and I cannot forgive Jamie for pretending he was different; for pretending, as he ripped up basil with his bare hands and told men, yeah, you can cook, that he was my mate. (That is the evil of television. Fake intimacy.) The dish may have been called Jamie’s Plank, but I do not remember. I hope it was. It should have been, even if the plank was me.

Barbecoa 2, then: it is neurotically vast, on two floors. London restaurants are big these days: what are they trying to say? Do they even know? Are they preparing to solve the housing crisis? Or is it a competition between chefs who have yet to experience Freudian psychoanalysis, and so think: ‘Who can build the biggest and stupidest brasserie-style abyss in which credulous diners can waste their money?’

It is next to Bafta, and opposite Pret a Manger. There is a menu in the street on a tiny plinth, as if we are outside a bad Venetian restaurant. Inside, the design is a queasy, unconvincing Art Deco, which makes Barbecoa look like every other giant restaurant that has opened in London in the past two years. It overlooks the church of St James’s: a pretty view of street-food stalls and street homeless, utterly wasted. It is, on a weekday lunchtime, almost empty: there are five tables of men and a baby. It is Vladimir Nabokov’s fish tank.

And I think, even before the food arrives, this restaurant is generic, and it is a mistake. You may not like a brand — and after the plank, I do not — but it must be coherent. Nobody goes to Jamie Oliver for fine dining — to eat the love child of Jamie Oliver and Alain Ducasse — but this is what he attempts here, or half-attempts, as if he does not trust himself, and he is right. The brand falters, and that is what we eat on a banquette by a window: a failing brand.

So, chicken wings: they are buried in an evil orange batter, they do not taste fresh, and they stay on my tongue all day, which is unpleasant. Lamb chops — for £26 — are chewy and greasy and plentiful. A sirloin — for £32 — is adequate, which is not good enough in a city full of dedicated steak restaurants; you would do better in Hawksmoor, the barn across the road, or at Beast.

It is a shame that a steak restaurant excels in vegetables, but Barbecoa does: the dauphinoise potatoes and creamed spinach are the best thing we eat, aside from the bread. Inevitably, it is sourdough. Sourdough has conquered London, as so many have before it. It comes with a weird chicken butter which I do not want to eat, and I no longer know what Jamie Oliver is for.