Arguably the inventors of the British gastropub, the Eyre brothers have now opened a stylish, grown-up restaurant

Ten years ago, David Eyre opened what is widely regarded as Britain's first gastropub, The Eagle in Farringdon, London. It was a smart move to set up next door to a newspaper office; The Eagle became the unofficial staff canteen for Guardian journalists, and news inevitably travelled about this dream pub, with its adventurous repertoire of Spanish and Portuguese dishes.

Eyre later sold his share in The Eagle to his partner, and headed east, with brother Rob, to open Eyre Brothers, a gourmet sandwich bar and takeaway in the heart of bohemian Shoreditch. Now the Eyres have upped the ante dramatically with a 110-seater restaurant, which is easily the most grown-up yet to open in Shoreditch, and a signal that an area that was once up-and-coming has now well and truly arrived.

Located in south Shoreditch, where the City begins – an area known to the property developers as SoSho, revoltingly enough – the new restaurant is a big, confident project, obviously designed to appeal as much to bankers as to website designers. A former warehouse has been stylishly kitted out in dark wood and conker-coloured leather. Lining one side of the room are an open kitchen and a bar counter. There's a comfortable lounge-bar area, also serving food, and floor-to-ceiling windows over a classic Shoreditch vista of loft conversions, scaffolding and scurrying estate agents.

The main challenge presented by the restaurant lies in mustering an appetite after totting up how much a flat bought in the area five years ago would now be worth. Still, if any menu can help, this one will. A seductive mix of the familiar and the exotic, it gathers dishes from Spain, Portugal and Italy and gives them a contemporary polish. The style is recognisably that of the recipes from The Eagle collected in David Eyre's recent book, Big Flavours and Rough Edges, though the edges have been smoothed off now that he's freed from the exigencies of a pub kitchen, and prices are inevitably higher than at The Eagle – starters range from £4.50 to £9.50, and main courses peak at £23.

On the evidence of a lunchtime visit, Eyre Brothers is already drawing in the media crowd; seated at neighbouring tables were newsman Jon Snow, whose trademark designer tie supplied the brightest splash of colour in the room, and gardening guru Monty Dont.

My own guest was Tony Quinn, who, as readers of his weekly film reviews in this newspaper will already know, is a man of many quirky and strongly held prejudices and obsessions. Among them is a phobia of what he calls "dirty food" – that is, any dish whose ingredients can't immediately be identified at a single glance. This tends to rule out any meal involving spices, pulses, sauces, marinades, or indeed anything which isn't grilled tuna. Fine restaurants such as Moro and The Real Greek have already fallen victim to his tyrannical whim. But Eyre Brothers passed muster; alongside such challenging combinations as grilled sardines in pancetta with salsa verde, or pork and clams, the menu also offers salade Nicoise, grilled leg of lamb and – yes – grilled tuna.

Tony began with a suitably ascetic Portuguese soup called canja, a clear chicken broth flavoured with lemon juice and mint, and containing rice and succulent slivers of chicken. Something about the broth's lemony aftertaste called to my mind the washing-up bowl, but Tony was enthusiastic. My own filetto freddo, ruby-rare slices of beef fillet with firm new potatoes and salad leaves in a sprightly dressing, was an assembly of first-class ingredients, precisely cooked. But what rendered it sensational was a garnish of tarragon, breadcrumbs, capers, and possibly ground almonds, an intensely-flavoured blast of anise, sourness and sweetness unlike anything I'd ever tasted.

Having been banned from ordering the grilled tuna, Tony followed up with the second plainest main course on the menu, an exemplary fillet of roast wild seabass, served with new potatoes and sweetly slow-roasted tomatoes. My choice of caldeirada – a Portuguese fish stew – was as rich and warming as a Mediterranean sunset. Monkfish, seabass, tender curls of squid and plump scallops were abundantly featured in a golden broth, fragrant with saffron and coriander. Splendidly pliable sourdough bread did soaking duties, along with a side order of slippery olive oil mash. But a second side-dish of Moroccan lentils was flavourless, the pulses tasting only of the parsley with which they were garnished. Still, they served to prompt a reverie from Tony about how George Gissing had survived on lentils for several years, the author of New Grub Street being another of his more regrettable obsessions.

After the inventiveness of the first courses, the pudding list looked fairly unexciting, but grilled figs with Amaretto proved to be a small masterpiece. Gentle heat had coaxed a vivid sweetness from the fruit, while allowing it to keep its uniquely sensual texture. Swooningly, I attempted to introduce a forkful of the pink, Amaretto-drenched flesh into Tony's mouth, but the Women In Love moment went slightly awry when he snatched the fork away and did the honours himself.

Big flavours, then, the Eyre Brothers offer in abundance, and they should feel justifiably confident that their new restaurant is going to become as much a fixture on the London dining scene as The Eagle. The only rough edges came with the service, which was pleasingly informal, but will really have to speed up if Eyre Brothers is to attract City types as well as Shoreditch bohos. Jon Snow had long since cycled back to his office when our bill (of around £50 a head) finally arrived. You can't still be waiting for your coffee at 3.30pm, when you're rushing off to appear on telly. Those of us planning to spend the rest of the afternoon watching it, however, were very happy to linger.

Eyre Brothers, 70 Leonard Street, London EC2 (020-7613 5346). Mon-Sat lunch 12-3pm, dinner 6.30-11.15pm. All cards except Amex and Diners Club. Wheelchair access