Les Deux Salons, 40-42 William IV Street, London, WC2

Is there any point in choosing a restaurant to review on the basis that it makes for a good yarn? Ghastly food, inept waiters and rooms with all the charm of a funeral parlour might be torture to sit through, but there's plenty of scope for comic complaints. But save for the fun of reading of a Fawlty Towers-like experience, is it much use for the restaurant-goer?

I am visiting Les Deux Salons with the almost copper-bottomed guarantee of top-quality food and environment. Its two big brothers, Arbutus and Wild Honey, are both exemplary. Arbutus burst on to the restaurant scene in 2006 with chef Anthony Demetre delivering very elegant dishes in an almost austere Soho room. He followed it in 2007 with Wild Honey, a diametrically opposed setting – all wood panelling and clubby atmosphere – where little copper pots of daubes and soups arrive at one's elbow to make it feel like everything's all right with the world.

Now Demetre and partner Will Smith give us Les Deux Salons – an airy brasserie affair just off Trafalgar Square. If the scale of the new venue is challenging – it must be six times the size of Wild Honey – then the location is some comfort. On the Saturday lunchtime I visit, there is a constant thrum of passers-by heading to Covent Garden or the National Gallery.

Open for just a few weeks, word is clearly already out: I can get only 12.30pm or 9.30pm sittings. With some reluctance, I opt for lunch with the children, rather than a rare romantic night out with Mr M. (I'm usually asleep by 10pm, to my shame.)

Mr Smith is working the front of house and seems to check in studiously on every table through the course of lunch service. Well, all except ours. Perhaps this is helpful. One, I don't have to pretend not to be the person he's seen having plenty of media-ish lunches in Wild Honey; and two, it makes me realise that one becomes less visible when eating with children – the proper test of a restaurant.

For an all-day venture in the heart of tourist London, families are key (I'd have thought) – and Les Deux Salons does offer a children's menu. And, greeting grumble aside, there's scarcely anything to find fault with. The cunningly aged rooms are beautiful – all fogged mirrors and faux-smoke-tinged walls. A pretty tiled floor and brilliant arrangement of tables that allows diners to feel tucked away, even in this large space, add to the splendour. And that's before we cast an eye over a menu full of brasserie classics such as omelette "Arnold Bennett", andouillette with mustard sauce, bouillabaisse and onion tart. Closer inspection reveals a few new-generation twists to keep repeat visitors happy. A salad of quince, wet walnuts and dolcelatte, for instance, or Cornish plaice stuffed with shrimps and kaffir lime.

Alas, although my children are pretty adventurous, the daughter spots a cheeseburger hidden among the items from the Josper charcoal grill (kitchen obsessives will be familiar with this sexy bit of kit). So she munches happily through that and some crisp chips (I manage to get a side-order of winter greens at her elbow, and she tucks into those, too). The son has warm salt-cod brandade with sauté of young squid-and-parsley cromesqui – now that's more like a budding critic – followed by bavette of Scottish beef with shallot sauce. "Just the right amount of chewy," is his verdict.

Mr M has ravioli of veal with fresh goat's curd and cavalo nero; I have traditional fish soup. The former is meltingly soft and savoury, the meat itself forming the parcels. My soup is somewhat oversalted, but that's the only bum note. The slow-cooked ox cheek with parsnip purée main is perfect – glossy and dark meat, smooth-as-silk purée and a side order of gratin dauphinoise that requires protection from the other diners with a sharp knife. Mr M's pork belly with lentils and autumn veg is properly fatty and falling apart.

We pool pudding resources with Paris-Brest with praline cream, glazed lemon tart and bitter chocolate mousse and come away deeply satisfied.

When we arrived, there'd been an air of newness (perhaps because we were one of just two tables occupied), but by pudding the joint is jumping and it feels as if Les Deux Salons has always been there (the horror of former tenant Pitcher & Piano a distant memory). Anthony Demetre and Will Smith have a hit on their hands – as if that were ever in any doubt.

8/10

Scores: 1-3 stay home and cook 4 needs help 5 does the job 6 flashes of promise 7 good 8 special, can't wait to go back 9-10 as good as it gets

Les Deux Salons 40-42 William IV Street, London WC2, tel: 020 7420 2050 Lunch and dinner daily. About £75 for two, including drinks and service

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Reviews extracted from 'Harden's London and UK Restaurant Guides 2010'. www.hardens.com