The act of opening a restaurant, being severely detrimental to both bank balance and mental health, should be done only sparingly over a lifetime. A fortnight ago, the team behind Medlar, a well-established, 15-year-old Chelsea fine dining spot, opened a sister restaurant, Cornus, in Belgravia. That seems to me an eminently sensible age gap, not least because the road to hospitality ruin is paved with overly keen expansion that leads to everything being spread far too thinly, be that the front of house or the praline cream. At Cornus, however, there is already a real sense of judicious growth in just about every aspect of this particular rollout. First, the location: Eccleston Yards is a genteel, prettily kept courtyard of shops about seven minutes’ walk from Victoria station. Leave the traffic and the hubbub behind, and slip down an alleyway into a former power station that’s been neatly coiffed, cobbled and filled with a Hotpod Yoga studio, a cryotherapy treatment boutique and a bespoke iced biscuit emporium. If that all sounds rather frivolous and not at all rooted in “the real world”, then I’ll remind you that this is Belgravia and the residents here rarely sully themselves with common reality. Cornus is in the far corner of the yard, down a marble passageway, and has its own elevator to take you up to the top floor, where it lives in all its white, starched tablecloth majesty – 70 seats in an L-shaped room with honey fabrics and floor-to-ceiling windows draped with ivory netting. The staff are lovely, smiley and very amiable, although the place itself is a somewhat serious restaurant. The menu, meanwhile, is seriously grounded in the principles of French cooking – executive chef Gary Foulkes has worked at high-end joints such as The Square and Angler. Begin with dainty starters of handpicked Devon crab with a smattering of hass avocado, wasabi and finger lime, or a warm salad of artichokes, crispy quail’s eggs, summer beans and black Australian truffle. Move on to mains of roast Newlyn cod with persillade of Scottish girolles, grilled cuttlefish and Alsace bacon; or southdown lamb, romero pepper piperade, lamb kofte, fried capers and olives. Both of those main courses dance around the £45 mark, so the prices here are serious, too. So serious, in fact, that a tomato salad, a small portion of spaghetti with lobster and a slice of lemon tart will set you back about £80 before you’ve even glanced at the wine list; there is a complimentary gougère and good focaccia from the bread basket, though. Obviously, I am majorly underselling those three dishes. That tomato salad is made with Hubert Lacoste’s exceptional and rare heirloom tomatoes from Gers in south-western France. Monsieur Lacoste, I hear, is terrifically picky about when his tomatoes are allowed to leave his farm – so much so that only on his say-so, and not a moment before, can Foulkes even consider adorning them with goat’s curd, dressing them in cherry juice and tweezering fig leaves on top. Hubert’s tomatoes cost £20, although in the interests of transparency I paid less than that, because I visited when Cornus had only just opened. The £38 lobster spaghetti consists of delicate, hand-rolled pasta, native lobster, Amalfi lemon and a small scoop of oscietra caviar. Yes, the price is steep, but then hand-rolled spaghetti in Belgravia has never come cheap. The Amalfi lemon tart with greek yoghurt ice-cream may well be £17.50, but it’s made by Kelly Cullen, one of the UK’s brightest new names in desserts, and Cornus has cleverly snapped her up as its pastry chef, much to my chagrin because beforehand she was at Allegra, one of my locals in east London. Here, her raspberry millefeuille with lemon verbena cream and baked raspberry ice-cream is one of the highlights of the entire Cornus menu. This is not a raucous place to dance on tables or to look for all-day brunch, or indeed to leave stuffed to the gills. It’s a modern, yet defiantly old-school restaurant where you can speak, be heard and be well looked after. It isn’t trying to be youthful or on-trend, it’s just celebrating exquisite products cooked by a talented team working at a level that only a handful of people in Britain today could even hope to manage. When I visited, most of the clientele seemed to be Medlar regulars, happily ensconced in their new lunch venue, nibbling quails’ eggs and chocolate barquette. Big prices, nice tablecloths, no riff-raff: to your average Belgravian punter, that is as good as it gets. Cornus 27C Eccleston Place, London SW1, 020-3468 8751. Open Tues-Sat, noon-3pm & 6.30-10pm. From about £80 a head à la carte, plus drinks and service Listen to the latest episode of Grace’s Comfort Eating podcast here This article was edited on 16 August 2024, to correct the price of the tomato salad – an earlier version had it listed at £24.