Rose Gray died in February this year but the River Café, which she created with Ruth Rogers, goes marching on.

Uncompromisingly committed to simple excellence, the pair chose never to open any more branches, instead concentrating on getting the one place as right as it could be. But a happy result of this dedication, supplemented by their wonderfully approachable cookbooks, is that a whole generation of cooks, both professional and domestic, have carried the River Café’s principles out into the wider world. Nobody has had greater influence on how we eat in recent years — and you don’t have to have made the pilgrimage to Thames Wharf to have reaped the benefits.

Trullo, named after the daft conical houses in Apulia, has been opened by Jordan Frieda, formerly front-of-house at the River Café itself, and Tim Siadatan, in 2002 the star of the first Jamie’s Kitchen, following a bunch of apprentice chefs at Fifteen, Jamie Oliver himself being an early River Café escapee. Siadatan, originally from Reading, has subsequently worked at Moro, another outfit inspired by RC values.

The site used to be the Gill Wing Café, an outpost of the kitchen, jewellery and shoe shops group located a few hundred yards away on Upper Street. But once you’ve gone round Highbury Corner, it’s a rougher ambience, Islington values faltering a little more every 50 or so yards. Trullo, however, is such a draw that it’s obviously going to triumph over this slightly challenging micro-climate.

The premises have been tastefully re-decorated, thick navy gloss outside, sombre tones inside too, with dark matt green paintwork on the lower level, white walls above. There’s a pretty glazed wall cabinet, some rustic upper shelves, and a sideboard displaying a bowl of superb Sicilian lemons. The paper-covered tables are packed in tight and the kitchen, where Siadatan produces impressively with just a couple of assistants, would be open were it not around the corner of this L-shaped space.

Despite his youth, Frieda is a remarkably confident host-patron, almost single handedly creating an easy-going mood, enhanced by a retro soundtrack. On Friday night, the clientele seemed Soho-ish for the location and gay; on Tuesday, it was more blue-striped shirts; all clearly pleased to be there — the price-quality ratio is quite amazing.

The menus change daily, using ingredients in season, presented simply. Everything we tried, in two visits, was good. Ravioli verde with homemade ricotta and sage butter (£5 for a starter portion) were fantastically fresh. Tagliarini with brown shrimps, zucchini, butter and chilli (£6) was fairly hot (a bit of a Jamie taste there?) but suffused with the taste of the shrimps, so much more rewarding than prawns in a dish like this, and made colourful by a mixture of yellow and green courgette strips.

Bucatini with lemon (£4.50) was the classic River Café version, a simple dish combining lemon juice and zest, olive oil, parmesan and basil leaves, absolutely perfectly done, tangy and refreshing, a great summer starter.

There’s a fierce charcoal grill here that Siadatan uses to good effect for many of the mains. Chargrilled wild sea trout, fresh peas, Castellucio lentils and aioli (£13) came crisped on the outside, pleasingly undercooked inside, with the slippery lentils and crunchy peas nicely mixed up, lifted by the fierce garlicky and lemony mayonnaise. A chargrilled whole mackerel (£12.50) seemed at first glance overcooked but it turned out to be smokily delicious too, well accompanied by some intact sprigs of salty samphire.

Ovenbaked slip soles (£13.50) was a generous serving, two whole, trimmed fish, yielding lots of sweet, firm fillet, served with proper tangled-up, substantial spinach and fresh, skinned broad beans — simple, classic, lovely. Siadatan seems especially good with pesce.

Puddings delivered too. Vanilla pannacotta with grappa (£4.50) tasted fantastically luxurious — best not to think about all the double cream that goes into it — and looked exactly as per the River Café illustration, speckled with vanilla seeds, although sadly minus the raspberries Rogers and Gray suggest. An unsweetened melon granita (£4.50) was a healthier option, still vibrantly fruity.

All these prices are less than half what the River Café itself charges for equivalent dishes. What more could you ask from a neighbourhood local? That they don’t recoup viciously on the wine? There’s a great Italian list here with not a single bottle marked up more than £10 — the cheapest wine, a Sicilian Catarrato at £15 a bottle, is ideal summer drinking, light and crisp. Trullo also presents a bill without service included, heroically.

If you really wanted to be snippy, you could still carp about the whole River Café phenomenon of Italian restaurants being run by non-native Italians, as though to say: we can do it better. Not me. We can, sometimes. The only downside with Trullo is that it will surely be packed out. Best keep this one secret?