Russell Sage Studios have designed the two floors of cosy, slightly crowded, conviviality

39 James Street, London W1U (0207 993 3257)

A friendly Madrileno told me that the common house-fly was the inspiration for the tapas phenomenon. In rough restaurants of Castile and Galicia, patrons drinking at the bar used to be bothered by flies crash-landing in their wine; so they used to cover the glass with a coaster. One day, someone asked the chef to bung him a gherkin to put on the coaster. Later the cardboard plate could carry a bit of cheese, a cut of pork loin or a morsel of morcilla (fried black pudding) … and the Spanish hors d'oeuvre was born. It's graduated since then to greater heights of sophistication but essentially remains a series of fancy snacks for chatty, wine-swilling compadres to share.

I've been to dozens of tapas bars and seen the concept debased to mean a restaurant serving lots of dishes on small plates, to be eaten with knife and fork – the equivalent of having five or six starters and paying large bills for doing so.

Social Wine & Tapas is the best tapas joint I've ever encountered outside Spain, because it gets the emphases right: this is, basically, a very fancy wine bar with a long menu of small dishes to share while trying umpteen wines in small 125ml servings. It's the latest offering from the world-conquering Jason Atherton, who started life at Gordon Ramsay's Maze, and opened his own account with Pollen Street Social in 2011, which spawned Little Social, City Social and Social Eating House. In 2013 he opened the Berners Tavern, the most beautiful dining-room in London. The Athertonian empire has spread to Singapore, Hong Kong, Dubai – and New York where he's just opened at Edition, one of Ian Schrager's hotels. But at this tapas joint he's taking a back seat.

The brains behind the operation is his long-time sommelier, Laure Patry, a charming, omnicompetent dame from Le Mans. After 10 years setting the wine lists for the Social chain, in here she's boss, maître d', waitress and wine wrangler, while the food menu is devised by Frankie Van Loo of the Social Eating House. Mme Patry is responsible for odd little touches, like the tape-loop voice giving a lecture on wine maintenance that greets you in the lavatory, and the generic funk on the PA system. Russell Sage Studios have designed the two floors of cosy, slightly crowded, conviviality with lots of wood, industrial-chic ceilings, black metal bars and leather: it's like being inside a cigar box crossed with a correctional facility.

My gourmet friend Chris Hirst and I were told to try one shared dish from each of six courses – Hams, Cheese, Eggs, Vegetables, Fish and Seafood, and Meat. We tried to be polite, but soon abandoned all restraint and tried everything in sight.

We began with an orgy of piggery jiggery-pokery: Basque-region ham croquettes resembling arancini balls, a jamon-manchega toastie with quail's eggs (basically a croque monsieur with a touch of Brideshead), Cecina salami and fat slices of Iberico bellota derived from acorn-fed porkers in the mountains around Seville. The hams came arrayed on little metal trays clamped to the side of the table, a nice touch. Under Laure's direction we drank a lightly perfumed Clos de L'Elu from Anjou, which danced a tarantella around all the hammy splendour.

Slow-cooked egg with oxtail dashi and creamed potato failed to impress – both egg and potato too runny and the Japanese dashi, a sauce involving seaweed and smoked bacon, lacked salience – but panfried duck egg with confit leg and cassoulet was deliciously upbeat. From the vegetables, we chose chargrilled carrots with burnt aubergine, miso and walnut pesto. Ho-hum, I thought, how boring this will be – but it was stunning, the truncheon-sized carrot a miso-flavoured, nut-crunchy delight, the aubergine divine.

The fish selection brought Szechuan fried chipirones, tiny squid deep-fried with togarashi dried chillis, to be given a squeeze of lime and dipped in a dark-green squid-ink aioli sauce. Less exotic roasted cod was firm and succulent but the advertised accompaniments of fennel and anchovy weren't apparent.

To be honest I didn't care much, having fallen in love with a 2006 Campanian red, fermented in chestnut barrels and saucily entitled Nude Aglianico. It went well with the climactic meat dish of Norfolk suckling pig, perfectly cooked, its skin glowing with sherry caramel, while an attendant lord of roasted pineapple provided a surprisingly delicious harmony.

Only a madman would have eaten anything else after this feast, but, as a connoisseur of burnt cream, I had to try the crema Catalana. It was the best crème brulee I've ever tasted, seared segments of orange meeting blobs of orange puree on heavenly orange cream, all for five quid. For that alone I'd come back to this excellent two-storey boite of Elysian snacks, served up by a talented Frenchwoman who can genuinely bring you what Withnail once demanded: the finest wines in Creation.

Food ****
Ambience ****
Service *****

39 James Street, London W1U (0207 993 3257). Around £28 per person, before wine and service